Life Cycle Assessment - ArcelorMittal Sections

CTBUH Research Report

Life Cycle Assessment of Tall Building Structural Systems

Dario Trabucco, Antony Wood, Olivier Vassart, Nicoleta Popa, and Donald Davies

© Council on Tall Buildings and Urban Habitat

Life Cycle Assessment of Tall Building Structural Systems

Dario Trabucco, Antony Wood, Olivier Vassart, Nicoleta Popa, and Donald Davies

Research Funded by:


Research Funded By:

Bibliographic Reference: Trabucco, D., Wood, A., Popa, N., Vassart, O. & Davies, D. (2015) Life Cycle Assessment of Tall Building Structural Systems. Council on Tall Buildings and Urban Habitat: Chicago. Principal Research Investigators: Dario Trabucco, Antony Wood, Olivier Vassart, Nicoleta Popa & Donald Davies Additional Researchers: Meysam Tabibzadeh, Eleonora Lucchese, Mattia Mercanzin & Payam Bahrami Editorial Support: Jason Gabel Layout: Mattia Mercanzin & Marty Carver

Published by the Council on Tall Buildings and Urban Habitat (CTBUH) in conjunction with ArcelorMittal © 2015 Council on Tall Buildings and Urban Habitat Printed and bound in the USA by The Mail House The right of the Council on Tall Buildings and Urban Habitat to be identified as author of this work has been asserted by them in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988. All rights reserved. Apart from any fair dealing for the purposes of private study, research, criticism or review as permitted under the Copyright Act, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form by any means, electronic, mechanical, photocopying, recording or otherwise, without the written permission of the publisher. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data A catalog record has been requested for this book ISBN: 978-0-939493-48-7

Council on Tall Buildings and Urban Habitat S.R. Crown Hall Illinois Institute of Technology 3360 South State Street Chicago, IL 60616 Phone: +1 (312) 567-3487 Fax: +1 (312) 567-3820 Email: [email protected] www.ctbuh.org www.skyscrapercenter.com CTBUH Asia Headquarters Office College of Architecture and Urban Planning, Tongji University 1239 Si Ping Rd, Yangpu District, Shanghai, China 200092 Phone: +86 21 65982972 Email: [email protected] CTBUH Research Office Iuav University of Venice Dorsoduro 2006, 30123 Venice, Italy Phone: +39 041 257 1276 Email: [email protected]

Front Cover: Image sources; Clockwise from top left: FreeImages.com/Bo de Visser; Marshall Gerometta, (cc-by-2.0) U.S. Army Materiel Command, mzacha via RGBStock, FreeImages.com/steph poitiers


Principal Researchers / Authors Dario Trabucco, Research Manager, CTBUH / Iuav University of Venice Antony Wood, Executive Director, CTBUH / Illinois Institute of Technology / Tongji University Olivier Vassart, Head of Global R&D Long Carbon, ArcelorMittal Nicoleta Popa, Senior Research Engineer, ArcelorMittal Donald Davies, Principal, Magnusson Klemencic Associates Additional Researchers / Contributors Eleonora Lucchese, CTBUH Research Office, Venice Mattia Mercanzin, CTBUH Research Office, Venice Meysam Tabibzadeh, CTBUH Research Office, Chicago Payam Bahrami, CTBUH Research Office, Chicago

Contributors / Project Steering / Peer Review Panel Mark Aho, McNamara / Salvia Peyman Askarinejad, Arabtec Martina Belmonte, CTBUH/IUAV Joseph Burns, Thornton Tomasetti Luis Simoes Da Silva, University of Coimbra Edward DePaola, Severud Associates Chukwuma Ekwueme, Weidlinger Associates Paul Endres, Endres Studio David Farnsworth, Arup Rolf Frischknecht, Treeze Erleen Hatfield, Buro Happold Ben Johnson, Skidmore, Owings & Merrill Leif Johnson, Magnusson Klemencic Associates Makoto Kayashim, Taisei Raffaele Landolofo, University of Naples Dennis McGarel, Brandenburg Declam Morgan, Buro Happold Levon Nishkian, Nishkian Menninger Tatsuo Oka, Utsunomiya University Arif Ozkan, Arup Stefano Panseri, Despe John Peronto, Thornton Tomasetti Dennis Poon, Thornton Tomasetti Christopher Rockey, Rockey Structures Ronald Rovers, RiBuilIT Tim Santi, Walter P Moore Allen Thompson, WSP Robert Victor, Brandenburg John Viise, Thornton Tomasetti Wolfgang Werner, Urban Fabrick Yong Wook Jo, Arup Nabih Youssef, Nabih Youssef & Associates


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Contents

About the CTBUH About ArcelorMittal About the Authors

6 6 7

Preface 1.0

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Tall Buildings Today 1.1 Role of Structural Systems in a Tall Building 1.2 Review of Current Structural Systems in Tall Buildings 1.3 Foundation Types

2.0 Sustainability and Tall Buildings 2.1 Energy Consumption of Tall Buildings 2.2 Embodied Energy of Tall Buildings

12 14 16 21 24 27 30

3.0 Life Cycle Assessment 32 3.1 Explanation of ISO LCA 34 3.2 Definition of the Goal of the Study 35 3.3 Scope Definition of this Study 36 3.4 Scenario Analysis and Identification of 37 Functional Units 3.5 System Boundaries 40 3.6 Structural Systems and Materials 40 3.7 Floor Systems used 40 3.8 Inventory of Materials 41 4.0

Steel: Cradle to Grave 4.1 Steel Production 4.2 Structural Steel Profiles 4.3 Steel Plates 4.4 Steel Fabrication 4.5 Steel Rebar 4.6 Welded Wire Fabric 4.7 Metal Decking 4.8 Steel Production Inventory Data 4.9 Life Phase 4.10 Recycling

44 46 48 48 49 50 51 52 53 54 55

5.0

Concrete: Cradle to Grave 58 5.1 Cement Production and Transportation 60 5.2 Cement Substitutes 61 5.3 Gravel, Sand, and Aggregates 64 5.4 Concrete Production and transportation 65 5.5 Environmental Data for concrete 66 5.6 Recycling of Concrete and Aggregates 68

6.0 Fireproofing Materials: Cradle to Grave 70 6.1 Types of fireproofing materials 73 6.2 Environmental Impacts of Fireproofing Materials 74 7.0

Transportation and On-Site Energy Use 7.1 Transportation and On-Site Operations in Literature 7.2 Transportation 7.3 Crane Operations 7.4 Concrete Pumping 7.5 Formworks 7.6 Foundations

8.0 The End-of-Life of Tall Buildings 8.1 High-Rise Demolition Techniques 8.2 Impact of Structural Materials on the End-of-Life of Tall Buildings 8.3 Energy Use in Demolition 8.4 Transportation Assumptions for Debris 8.5 Sources of Data on Tall Building Demolition 9.0

Inventory of Materials and Research Results 9.1 The Assessment of Two Environmental Impacts 9.2 Comments on the Selected Indicators 9.3 Research Results 9.4 Comparison with Literature Results 9.5 General Research Conclusions 9.6 Future Research

76 78 81 81 83 84 84 86 88 90 91 93 94 96 98 98 99 99 102 107

10.0 Appendix: Detailed Results of Each Modelled Scenario 112 Acknowledgements 178 Bibliography 179


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About the CTBUH The Council on Tall Buildings and Urban Habitat (CTBUH) is the world’s leading resource for professionals focused on the inception, design, construction, and operation of tall buildings and future cities. A not-for-profit organization, founded in 1969 and based at the Illinois Institute of Technology, Chicago, CTBUH has an Asia office at Tongji University, Shanghai, and a research office at Iuav University, Venice, Italy. CTBUH facilitates the exchange of the latest knowledge available on tall buildings around the world through publications, research, events, working groups, web resources, and its extensive network of international representatives. The Council’s research department is spearheading the investigation of the next generation of tall buildings by aiding original research on sustainability and key development issues. The Council’s free database on tall buildings, The Skyscraper Center, is updated daily with detailed information, images, data, and news. The CTBUH also developed the international standards for measuring tall building height and is recognized as the arbiter for bestowing such designations as “The World’s Tallest Building.”

Co u n c i l

on

Ta l l B u i l d i n g s

and

Urban Habitat

About the Research Funding Sponsor: ArcelorMittal With annual achievable production capacity of approximately 127 million tons of crude steel, and 222,000 employees across 60 countries, ArcelorMittal is the world’s leading steel and mining company. With an industrial presence in over 20 countries, they are the leader in all major global steel markets including automotive, construction, household appliances and packaging, with leading research and development and technology, sizeable captive supplies of raw materials, and extensive distribution networks. ArcelorMittal uses their researchers’ expertise in steel to develop cleaner processes and greener products, including ultra-high-strength steels (UHSS) and Ultra-Low CO2Steelmaking (ULCOS), to make steel production more sustainable and help reduce both their own environmental impact and that of their customers.

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About the Authors Dr. Dario Trabucco, PhD Research Manager, Council on Tall Buildings and Urban Habitat / Researcher, Department of Architecture Construction and Conservation, Iuav University of Venice Venice, Italy Dario Trabucco is a tenured researcher in Building Technology at Iuav University of Venice, Italy. From March 2013 to February 2014 Dario was a research associate at the Council on Tall Buildings and Urban Habitat/Illinois Institute of Technology, primarily working on the funded research project “A Whole Life Cycle Assessment of the Sustainable Aspects of Structural Systems in Tall Buildings.” In 2014, he assumed the role of CTBUH Research Manager and established the CTBUH Research Office in Venice. Since then, he has acted as Principal Investigator for two additional sponsor-funded research initiatives by the CTBUH, “A Study on the Architectural and Engineering Properties of Composite Megacolumns” sponsored by ArcelorMittal and “A Study on the Damping Technologies Available for Tall Buildings: Comfort and Safety,” supported by Bouygues Construction.

Dr. Antony Wood, PhD, RIBA Executive Director, Council on Tall Buildings and Urban Habitat / Research Professor, Illinois Institute of Technology / Visiting Professor, Tongji University, Shanghai Chicago, USA Antony Wood has been Executive Director of the Council on Tall Buildings and Urban Habitat since 2006. He is responsible for the day-to-day running of the Council in conjunction with the Board of Trustees, of which he is an ex-officio member. Prior to this, he was CTBUH Vice-Chairman for Europe and Head of Research. His tenure has seen a revitalization of the CTBUH and an increase in output and initiatives across all areas. Based at the Illinois Institute of Technology, Chicago, Antony is also a Research Professor in the College of Architecture at IIT, and a visiting professor of tall buildings at Tongji University Shanghai. A UK architect by training, his field of speciality is the design, and in particular the sustainable design, of tall buildings.

Nicoleta Popa Senior Research Engineer, ArcelorMittal Luxembourg City, Luxembourg Nicoleta has been involved in, managed and coordinated internal and European research projects, with partners and subcontractors coming from all over Europe, USA and China. Each research project aims at achieving deliverables such as: new products and solutions, standards/codes/regulations/technical agreements, design aids, as well as promotional materials and campaigns. Her expertise includes: fire design, composite construction, composite bridges, cost optimization, sustainability and building physics. She has ensured the dissemination of research results through seminars, conferences, distribution to engineers and architects as well as through papers in scientific publications, conferences, and seminars.

Professor Olivier Vassart Head of Global R&D Long Carbon, ArcelorMittal Luxembourg City, Luxembourg Olivier Vassart graduated as a Structural Engineer from the Polytechnic School of Louvain in Belgium. He also completed a PHD in Fire engineering at the University Blaise Pascal in France. Since 2002, he has worked for ArcelorMittal, where he is now a member of the Board of Directors of ArcelorMittal Global R&D in charge of the Long Carbon Sector. As well as his activities for ArcelorMittal, he is Professor of Steel and Composite Structures at the University Catholic of Louvain in Belgium and he is also an Invited Professor at the University of Ulster Firesert Northern Ireland.

Donald W. Davies, P.E., S.E. Senior Principle, Magnusson Klemencic Associates Seattle, USA Donald Davies is a Senior Principal at Magnusson Klemencic Associates (MKA). He leads MKA’s Hospitality and High-rise Residential work, as well as MKA’s Sustainability Committee. Don is a CTBUH advisory group member; and a founding board member of the Carbon Leadership Forum, an academic/professional collaboration focused on carbon-reduction strategies in the built environment. Over his 25-year career, Don has designed buildings up to 105 stories tall, with projects in more than 31 US cities and 16 countries.


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Preface Despite the history of the skyscraper spanning well over a century, and the fact that the world is now constructing tall buildings in excess of 1,000 meters in height, with the exception of the events of 9/11, we have never actually demolished or dismantled a building taller than 187 meters. That building was the Singer Building, a 187-meter tower in New York City that was demolished in 1968 to make way for 1 Liberty Plaza. The reality is that we are now building many hundreds of skyscrapers – in addition to those already in existence – with little idea about their real longevity, what variances and experiences they will have during their whole life cycle, and what will happen to them at the end of that life cycle. These are massively important issues that should influence the design of all skyscrapers from the very outset (i.e., how to design buildings for multiple changes in function, an indeterminate future, or even perpetual existence?), but the industry does not even have a template for assessing the relative implications – energy or otherwise – of the different stages of a building’s life. In the sustainability realm, emphasis has been placed on the reduction of operational energy at the expense of all other facets. While the reduction of operating energy is vitally important, it is far from the complete picture. Reducing the embodied energy of the materials in the building itself is equally important. As technologies increasingly allow buildings to move towards carbon-neutral operation (though we are still far away from that holy grail), embodied energy will become the main energy consumer, and thus it is the most critical area for further consideration now. In short, the true environmental impact

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of the full life cycle of tall buildings is a significantly unknown quantity. This is the point of departure for this guide, and the three-year research project that underpins it. A Life Cycle Assessment (LCA) is a methodology that gauges the consequences of human actions by analyzing the flow of materials used in a product or a building and traces the environmental impacts linked to each stage of its life cycle. An LCA thus begins by analyzing the effects of material extraction and processing, accounting for the specific pieces of equipment used and the energy needed to turn raw materials into a final product (in this case, a building). The assessment also evaluates the impacts of manufacturing, transportation, and on-site construction activities, taking note of both power consumption and carbon emissions during each process. Finally, operational activities, demolition, and end-oflife recycling are considered. When information from each stage is combined, a holistic picture of environmental impacts can be formed for a given product, one that acknowledges the various actions that are required to bring a single entity into existence through contemporary means. The true benefits of the LCA methodology are realized when numerous assessments are performed for different versions of a product. This allows researchers to compare alternatives along various impact categories, and provides a basis for making informed decisions that produce the greatest environmental benefits over time. Given this fact, it is clear that Life Cycle Assessment is largely the missing piece in the sustainable puzzle for tall buildings.

This research, which was undertaken by the CTBUH Research Division and sponsored by multinational steel manufacturer ArcelorMittal, identifies and compares the life cycle implications for multiple comparative structural systems found in 60- and 120-story buildings. Structural systems are by no means the entirety of a tall building, and an LCA of the components that are more likely to change over time (façades, MEP systems, interior fit out) would also be extremely valuable. However, the means to evaluate life cycle energy is still in its infancy and is an especially complicated subject. Thus, for this first study, focusing on the structural systems of a building – which accounts for a large share of the material inventory and has major impacts on all aspects of building performance – seemed a sensible choice. This report thus represents the first-ever full LCA on tall building structural systems ever performed, and represents a “first stab” at environmentally quantifying the decisions made in the design and engineering process of skyscrapers. Using the results found herein, industry professionals and researchers can recognize the performance of these systems along two key impact categories: Global Warming Potential (GWP) and Embodied Energy (EE). Global Warming Potential is measured by calculating the amount of carbon (or carbon equivalent) that is released over the course of a structure’s life cycle, allowing impacts on climate change to be determined. Embodied Energy was selected as an indicator for natural resource depletion, since the amount of energy consumed over the lifetime of the structural systems and their materials has direct implications


for the consumption of electricity, fossil fuels, and natural gas. In addition to this report’s ability to serve as a reference in the design process, it also serves as a launching point for further research into the life cycle of tall buildings. Indeed, as is typical with undertakings of this nature, more questions tend to arise than answers. From the outset, it was the Council’s goal to explore this topic with an emphasis on finding where further investigation is needed. Suggestions for further research are thus provided at length in the final section of the report. As evidenced in this study, the CTBUH Research Division plays a very important role, not only in achieving the Council’s mission of disseminating information on tall buildings to professionals and stakeholders around the world, but to engage in the global debate on sustainability that has relevance far beyond the industry itself. The CTBUH is well-positioned for research such as this due to its intermediary role between a diverse set of professionals, with members and contributors ranging from architects, engineers, material specialists, owner/ developers, city planners, construction companies, and equipment suppliers. The Research Division is one of the ways that the Council uses these resources to address the research gaps identified in the Roadmap on the Future Research Needs of Tall Buildings, a 2014 CTBUH publication that lists and prioritizes topics that are in greatest need of further exploration. By focusing the efforts of the CTBUH in this way, attention is brought to often ignored or underrepresented aspects of tall buildings, mobilizing individuals to obtain a more complete understanding of the industry.

The daunting complexities of life cycle research require the collaboration between numerous individuals within varying specializations. This LCA alone drew on the support and expertise of numerous companies, all of whom are acknowledged on page 178. Thus, this project is truly an indication of concern for many in the tall building industry regarding the “big picture” of sustainability for our cities. So let this report serve not only as a plunge into an emerging field of study, but a call to action that emphasizes the importance of looking at the consequences of our choices, from beginning to end. Antony Wood Chicago, USA Dario Trabucco Venice, Italy


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1.0 Tall Buildings Today


1.0 Tall Buildings Today

The Council on Tall Buildings and Urban Habitat (CTBUH) recognizes three different ways of defining a tall building. According to the CTBUH, tall buildings exhibit some element of “tallness” in one or more of the following categories: •

Height Relative to Context: a building is taller than those in the surrounding area with respect to a prevailing urban norm;

•

Proportion: a tall building has a slender appearance made evident by a relatively small base in comparison to its height;

•

Tall Building Technologies: a building contains technologies which may be attributed as being a product of its height (e.g. specific vertical transport technologies, structural wind bracing as a product of height, etc.).

Figure 1.1: Home Insurance Building, 1885, Chicago, generally accepted as the first tall building because of its curtain wall construction on a steel frame.

In addition to the above criteria, there are two definitions that establish universal height thresholds for tall buildings: the CTBUH defines “supertall” buildings as those over 300 meters in height, and “megatall” buildings as those over 600 meters in height. Although great vertical strides are currently being achieved by an increasing number of tall buildings every year, there are only 93 supertall and three megatall buildings completed and occupied globally as of June 2015. The birthplace of the tall building typology is still a heavily debated topic among experts. However, it is commonly agreed that the first tall buildings in history were found in New York and Chicago (Barr, 2014). An early observation by Fryer (Fryer, 1891) mentions three basic elements that contributed to the birth of skyscrapers:

12 | Tall Buildings Today

Figure 1.2: Equitable Life Building, 1870, New York, considered by some to be the first tall building in history due to its exploration of the potentialities offered by the passenger elevator Source: (public domain) Emerson7


the modern passenger elevator, the invention of iron/steel structures (see Figure 1.1), and the terracotta flat arch element to protect horizontal iron beams from fire. Rem Koolhaas (Koolhaas, 1978), almost one century later, also cites steel frameworks and the passenger elevator as the elements that made the construction of tall buildings possible. Both of the above definitions exclude several notable examples of buildings that, despite having a load bearing masonry wall system (such as the 1893, 17-story Monadnock Building in Chicago), can clearly be considered a tall building (Leslie, 2013). Considering this argument, the elevator is the only remaining determinant for a tall building. In this case, the Equitable Life Building (see Figure 1.2), completed in New York in 1870, would be the first tall building in the history due to its exploration of the potentialities offered by the passenger elevator (Weisman, 1970).

Figure 1.3: Load bearing wall system for skyscrapers Monadnock Building, Chicago, (Floor Plan) Source: Leslie, Thomas (2013), “The Monadnock Building, Technically Revisited” CTBUH Research Paper, 2013 Issue IV, pp 29. Redrawn by CTBUH

The increased heights and different shapes that New York skyscrapers adopted as a result of the 1916 Zoning Resolution, which also affected the design of tall buildings in all other American cities (Willis, 1986), did not alter the basic structural schemes used since the birth of the skyscraper typology. In fact, from a structural perspective, all skyscrapers built before the Second World War are quite similar, and were based on the principle of a rigid frame, with required stability against lateral loads provided by the stiffness of beam-column connections (Ali & Moon, 2010) as well as the natural bracing effect provided by the solid façade panels. The solid decorated urban blocks used in early skyscrapers evolved since the 1950’s toward a more neat and transparent

style that spread all over the world in a movement known as the “International Style.” Even if virtually all tall buildings have a façade freed from any load bearing or structural function, the International Style marked an evolution in the performance of tall buildings. Fully glazed and sealed façades, introduced for the first time in buildings such as the Lever House in New York and the Commonwealth Building in Portland, Oregon, dramatically reduced the thermal inertia of buildings. This lead to an increase in the reliance on mechanical air conditioning and ventilation systems, together with the thermal inertia of the internal structure and surfaces. Glazed façades also significantly reduced the weight of tall

buildings, while also taking away the solid walls punctuated by small windows that provided bracing against lateral loads. As a consequence of this, and of the increasing height and slenderness of tall buildings, bracing functions were later transferred toward the interior by creating braced trusses around the elevator core. Thus, using these new features, the modern tall building typology was born. One of the earliest examples of these features can be found in the Seagram Building in New York. Since the end of the Second World War, tall buildings have spread from their country of origin, the United States of America, to become a global symbol of modernity and


Tall Buildings Today | 13

350 325 300

Average Weight of Steel [kg/m2]

250

200

Premium for height

150

125 100

50

00

10

20

30

40

50

60

70

80

90

100

Number of Stories

Figure 1.4: Graph illustrating the “Premium for Height” concept Source: CTBUH Redrawn on the basis of M. M. Ali & K. S. Moon (2007), “Structural Developments in Tall Buildings: Current Trends and Future Prospects,” Architectural Science Review, Volume 50.3, pp. 205-223

wealth in many countries, with landmark towers erected all over the world, from South America to Europe, and from Russia to Australia. However, US cities remained the testing grounds for tall buildings, at least until the 1970s, when cities in Asia began raising their financial districts towards the sky. This latter phenomenon was different from what happened 20 years earlier in Europe and South America. In fact, cities such as Tokyo, Hong Kong, Seoul, and many others started to build their own landmark towers, yet dozens of normal, functional skyscrapers were also built to accommodate new businesses and residences. In response to the demographic trends and booming economies of the 1990s, other countries started to develop significant tall building cultures: Philippines, Indonesia, and Singapore built their own vertical cities by adopting an American model. In the 2000s, while the echoes of the 9/11 terrorist attacks were questioning the future of tall buildings in the US, skyscrapers became a global phenomenon: China, United Arab Emirates, Panama, South Korea, Singapore, Qatar, Australia, Canada, Turkey, and other countries marked their presence in the skyscraper world with the development of many new tall and 14 | Tall Buildings Today

supertall buildings. During the same period, more conservative European cities also experimented with the construction of tall buildings (London, Madrid, Milan, Paris, Frankfurt, Moscow, Saint Petersburg, etc.), not as a dominant building type, but as unique, widely debated landmarks. Today (in 2015), more than 3,000 towers taller than 150 meters exist in the world and this number increases at an unprecedented rate, with one new tower opening for business every other day, mostly in Asian cities. 1.1 Role of Structural Systems in a Tall Building From a structural point of view, a tall building is simply a beam cantilever with its base fixed to the ground. The structural systems must provide resistance to vertical loads (the building’s weight and design loads) as well as shear and bending resistance to lateral loads caused by wind and earthquakes. Gravity loads do not affect tall buildings in the same way as low- or midrise buildings. Gravity loads can be

static (permanent) or dynamic (time dependent). Static loads include the weight of structural and non-structural elements and can therefore be calculated at the design stage. On the contrary, live loads are less predictable and their design values are defined by building codes, as they can be uniformly distributed or concentrated depending on the use of each space. As these values take a lot of safety factors into account, they are very conservative and tend to be overestimated. Considering that the vertical load design principles for tall buildings are not significantly different from standard buildings and they scale proportionally with the size of the building, they do not impact the design of various structural elements, except for the floor systems. What should be carefully considered in this case are the effects of lateral loads; mainly, seismic and wind forces. These two forces don’t follow a proportional progression with building height. Instead, their effects on structures increase exponentially as buildings get taller. Accordingly, a tall building is also defined by its structural consideration of horizontal forces over vertical forces. As a consequence, it is important to acknowledge the lateral resisting system of a tall building structure. During the 1960s, Fazlur Khan introduced the concept of a “premium for height” (Ali & Moon, 2010) (see Figure 1.4). Since floor system weight remains constant with a regular building plan, the ratio of floor weight to the number of floors remains constant as building height increases. At the same time, the size and number of columns must increase progressively toward the base of the building in order to transmit the gravity loads accumulated


on the floors above. Thus, considering only gravity loads, doubling the number of stories means doubling the weight and strength of the columns. However, when lateral loads are taken into account, the amount of materials used in columns must be increased even more. In this case, columns need to be heavier, going from the top toward the base, to resist lateral loads, and the weight of the lateral resisting elements should also be considered when calculating the weight/ gross area ratio. As the height of the building increases, the lateral drifts start to control the design of the structure, and the stiffness of the components becomes the dominant factor instead of their strength. Therefore, the need for appropriate structural systems, beyond the simple rigid frame, must be properly addressed in the design of tall buildings, accounting for the prominent loads and forces that differ depending on a building’s height. Many aspects should be carefully considered when addressing lateral loads, especially in the case of wind: strength and stability, fatigue, excessive lateral deflections, frequency and amplitude of sway (the resonance of building oscillations can create problems with an elevator’s hoist rope), and possible buffeting are some of these aspects. Additionally, wind can also affect the surroundings of a building. There can be wind acceleration nearby or annoying acoustic disturbances that can be heard from far distances. Overall, it is necessary to consider wind loads when determining the required strength and stiffness of building frames. The effect of wind on a building can be described as follows: when wind vortices are shed alternately first on one side and then on the other side of a

Figure 1.5: Woolworth Building under construction, 1913, New York City Source: (cc-by-sa) Bain News Service

building, impulses occur in a direction perpendicular to the downstream flow, alternating from left to right, in addition to the impulse in the along-wind direction. Therefore, in addition to a building’s superstructure, information on local wind conditions is required in order to determine the necessary strength and stiffness of wall elements, roof elements, and their fastenings. Looking at the seismic design of structures, as their degree-of-freedom increases, there is a higher number of significant modes to be taken into consideration and the response to seismic excitement becomes more complex. Tall buildings appear to be less flexible than

“...the ideal structure to withstand the effects of bending, shear and vibration is a system in which the vertical elements are located at the furthest extremity.”



Figure 1.6: Commercial style high-rise example: Home Insurance Building, 1885, Chicago Source: (cc-by-public domain) LX

Figure 1.7: Commercial style high-rise example: Guaranty Building, 1896, New York City Source: Terri Meyer Boake

Figure 1.8: International Style example: United Nations Secretariat Building, 1953, New York City Source: (cc-by-sa) ZeroOne

low-rise buildings and thus generally experience lower accelerations. On the other hand, when the attenuation of seismic waves is taken into account, longperiod components are not attenuated as fast as short-period components with the distance from a fault. Thus, taller buildings can experience more severe seismic loads than low-rise buildings that are located at the same distance from a fault. Overall, from a seismic design perspective, while members designed for vertical loads are able to provide the resistance required for the vertical aspect of the seismic loads, a dedicated lateral load-resisting system must be designed to withstand the inertial forces caused by ground motion.

are located at the farthest extremity from the geometric center of the building (Taranath, 1998), such as in a hollow tube. Here, the parameters that control the efficiency of the structural element’s layout are bending and shear rigidity. From the bending rigidity standpoint, the best solution would be to maximize the total moment of inertia of the overall structure, positioning columns at the corners along the outermost perimeter of the building. As far as shear efficiency is concerned, the ideal solution would be a continuous wall without openings.

architect and the developer (to maximize the real estate value of the building).

Strength and stiffness are the main parameters controlling the limiting factors of motion and vibration. With lateral forces being the driving parameter for the design of a tall building’s structural system, the ideal structure to withstand the effects of bending, shear, and vibration is a system in which the vertical elements 16 | Tall Buildings Today

The existing structural systems used in contemporary tall buildings stem from the basic principles described above. During the last 50 years, rigid frame systems adopted in older tall buildings evolved into different structural families that are used depending on a number of parameters including the size of the building, the magnitude of the external solicitations, the availability and cost of materials, and labor and stylistic decisions made by the

1.2 Review of Current Structural Systems in Tall Buildings From the first 12-story skyscraper born in Chicago in 1885, the Home Insurance Building, to the under-construction 1000 meter Kingdom Tower, structural systems for tall buildings move with the times, changing according to not only architectural styles, but also technical evolutions (e.g., vertical transportation systems, construction techniques, and mechanical services). The first phase of skyscraper evolution happened in the Midwestern United States, with Chicago at the epicenter. Economic drivers allowed the first tall buildings to develop in response to the ever-growing need for office space and high-value rentable areas. After the Great Chicago Fire in 1871, “Commercial Style” high-rise structures were characterized


Figure 1.9: Empire State Building under construction, 1930-1931, New York City Source: (cc-by-sa) Daniel Ahmad

by steel rigid frames clad with non-load bearing materials such as brick, terracotta, and glass windows (see Figures 1.6 and 1.7). This kind of structural choice became preferred over the use of conventional load-bearing masonry walls, which were considered outdated (as they were not fire resistant). As a result of this new structural system, a surge of skyscraper development began in New York City, resulting in significant achievements like the Chrysler Building (319 m, 1930), the Empire State Building (381 m, 1931) (see Figure 1.9), and the General Electric Building (196 m, 1931). Unfortunately, as the race continued into the 1950s and 1960s, no major technical advancements were developed. Since structural analyses at the time were still affected by many uncertainties, the buildings of that period were overdesigned. Aside from the efficient use of steel rigid braced frames, the amount of materials used in these buildings was excessive. The economic upturn after World War II revitalized the development of skyscrapers, and was accompanied by

the application of European modernist architectural practices. The use of steel rigid frames was then replaced by tubular forms. Led by the technological growth that supported the development of rational analysis systems, the adoption of structural tubes led to the development of the so-called “International Style” skyscrapers (see Figure 1.8). Major examples of this period includes the World Trade Center in New York (417 m, 1972) and the Willis Tower in Chicago (442 m, 1974). From the 1980s, a driving Postmodern architectural force guided tall structures towards the development of “mega-frames”, core-andoutrigger systems, as well as mixed steel and concrete structures. No longer is the International Style a dominant force, as a host of factors must now be taken into account in skyscraper development. The balance between innovation and consumption now involves practical requirements and site

conditions, the supply, transportation, and delivery of materials, preferred construction methods, and many others. These issues entail the need for designers to consider all of the identification factors typical of each job site from time to time (Balridge, 2008, March 3-5). Classifications based on different parameters were proposed by many authors. Probably one of the most renowned and highly adopted is the classification proposed by Mir Ali and Kyoung Sun Moon (Ali & Moon, 2010), which distinguishes interior structural systems from exterior structural systems. This classification is based on the distribution of the primary lateral loadresisting components across the building layout. Interior structures are those in which the lateral load resisting system is located on the interior of the building (called the core). Likewise, in an exterior structure, the lateral load resisting system is located along the building perimeter (see Figures 1.10, 1.12, 1.14 and 1.16).



80

Number of Stories

60

40

20

Frame

Shear Walls

Frame and Shear Walls

Framed Tube

Tube-in-Tube

Modular Tube

Figure 1.10: Classification of tall building structural systems by Fazlur Khan (concrete) Source: M. M. Ali & K. S. Moon (2007), “Structural Developments in Tall Buildings: Current Trends and Future Prospects,” Architectural Science Review, Volume 50.3, pp. 205-223. Redrawn by CTBUH

are effective for buildings up to about 35 stories.

The following structural systems can be defined as the first category, interior structures: •

Braced hinged-frames: Steel shear trusses and steel hinged frames are included in this type as they resist lateral loads via axial forces in the shear truss members. They are effective for buildings up to about 10 stories.

•

Rigid frames: A frame is considered rigid when its beam-to-column connection has sufficient rigidity to hold (virtually unchanged) the original angles between intersecting members. Rigid frames can be made up of either steel or concrete members. Moment-resisting frames are effective for buildings up to about 30 stories (see Figure 1.11).

•

Shear wall: These structures benefit from the presence of concrete single or coupled shear walls acting as lateral load resisting elements. They


•

Shear wall (or shear truss) – frame interaction systems: Shear walls are interconnected with a system of beams and columns (rigid frame). The frame deflects in a shear mode, while shear walls deflect in a bending mode. As the two systems coexist in the same building, they are forced to sway together. This results in an enhanced stiffness since the walls are restrained at the upper level by the presence of the frame, and vice versa at the lower levels where the shear walls are subjected to a smaller amount of sway. They are effective for buildings up to about 60 to 70 stories.

•

Outrigger structures: This structural system is characterized by the presence of a core (see Figure 1.13), either constituted by braced frames or shear walls, and horizontal cantilever outrigger trusses or

Figure 1.11: “Rigid-frame” example: Seagram Building, 1958, New York City Source: Marshall Gerometta


140

120

Number of Stories

100

80

60

40

20

Rigid Frame

Framed-Shear Truss

Belt Truss

Framed Tube

Truss Tube with Interior Columns

Bundled Tube

Truss Tube without Interior Columns

Figure 1.12: Classification of tall building structural systems by Fazlur Khan (steel) Source: M. M. Ali & K. S. Moon (2007), “Structural Developments in Tall Buildings: Current Trends and Future Prospects,” Architectural Science Review, Volume 50.3, pp. 205-223. Redrawn by CTBUH

girders connecting the core with the exterior columns. Lateral deflections and bending moments of the core are reduced when the building is subjected to horizontal loads as the outrigger opposes the rotation of the core, transferring tension and compression action to the windward and leeward columns respectively. They are effective for buildings up to about 150 stories. The following structural systems can be defined as the second category, exterior structures: •

Figure 1.13: Example of concrete central core and steel frame Source: Dario Trabucco

Tubes (framed tubes, braced tubes, bundled tubes, tube-in-tube): These systems are comprised of closely spaced columns placed in the building perimeter that are connected to deep spandrel beams at each floor level, arranging a three-dimensional system that uses the entire building perimeter to resist lateral loads. They

are effective for buildings up to about 110 stories, depending on the type (see Figure 1.15). •

Diagrids: If the vertical columns of a traditional tube structure are replaced with closely spaced diagonals in both directions, a diagrid is obtained. Diagrid structures provide both bending and shear rigidity without the need of a core. They are effective for buildings up to about 100 stories, depending on material (steel or concrete).

•

Exoskeletons: The exoskeleton represents a lateral load resisting system that is located outside of the building, away from the façade. They are effective for buildings up to about 100 stories.

•

Space truss structures: These are modified braced tubes with diagonals connecting the exterior to the interior instead of being located parallel to the façades in plan. They are effective



160

140

120

Number of Stories

100

80

60

40

20

Braced Hinged Frame

Concrete Rigid Frame

Steel Rigid Frame

Concrete Shear Walls + Steel Hinged Frame

Braced Rigid Frame

Concrete Shear Walls + Steel Rigid Frame

Concrete Shear Walls + Concrete Frame

Outrigger Structure

Figure 1.14: Interior structures Source: M. M. Ali & K. S. Moon (2007), “Structural Developments in Tall Buildings: Current Trends and Future Prospects,” Architectural Science Review, Volume 50.3, pp. 205-223. Redrawn by CTBUH

for buildings up to about 150 stories (see Figure 1.17). •

Megaframes: These structures include megacolumns, braced frames of large dimensions at the building corners, linked by multistory trusses. They are effective for buildings up to about 160 stories, depending on material (steel or concrete).

In this study, two ranges of height for tall buildings are analyzed in order to cover the most typical structural systems for high-rise buildings between 1961 and 2010 (data provided by CTBUH Journal, Issue II, 2010). The first range includes buildings 200 meters to 300 meters in height, or similarly from 50 to 60 stories. Of the 19 buildings within this threshold that were completed in the mentioned period of time, five of them present a framed tube structural system, five have diagonalized structures (trussed tube, diagrids, or braced frames), 20 | Tall Buildings Today

four use tube-in-tube structures, and four use a core and outrigger system, leaving only one hybrid structure example (combined use of two or more structural systems, e.g. diagonalized outrigger core). Most of these buildings were built with steel and were completed between 1960 and 1980, while few were built with concrete or composite. The second range includes buildings 400 meters to 500 meters in height, or similarly from 100 to 110 stories. Only eight buildings are found within this range, half of which were completed between 2001 and 2010 with composite structures (diagonalized, hybrid, core/outrigger, and tube in tube). The second half are represented by steel structures (bundled tubes or framed tubes) completed between 1961 and 1980. Looking at the presented data, some trends can be found: tall buildings between 200 meters and 300 meters mostly utilize a structural system

Figure 1.15: “Bundled tube” system example: Willis Tower, 1974, Chicago Source: Marshall Gerometta


160

140

120

Number of Stories

100

80

60

40

20

Concrete Framed Tube

Steel Framed Tube

Tube-in-Tube

Concrete Braced Tube

Steel Steel Diagrid Exo-Skeleton Braced Tube

Steel Bundled Tube

Concrete Bundled Tube

Steel Braced Tube w/o Interior Columns

Space Truss

Super Frame

Figure 1.16: Exterior structures Source: M. M. Ali & K. S. Moon (2007), “Structural Developments in Tall Buildings: Current Trends and Future Prospects“, Architectural Science Review, Volume 50.3, pp. 205-223 Redrawn by CTBUH

realized with tubes, typical of the period of time in which they were constructed. With an increase in height (400 to 500 meters), structural systems get more diverse, with core and outrigger systems along with hybrid structures playing an emerging role.

must be taken into consideration (Chew Yit Lin, 2001), among the most important of which are soil conditions, load transfer pattern, shape and size of the building, site constraints, underground tunnels and/or services, and environmental issues.

1.3 Foundation Types

There are two main types of foundations for tall buildings: shallow and deep, as described here below.

The high pressures imprinted on the ground by a tall building could originate some problems in the designing and in the construction of the foundations. They represent crucial elements in the design process, since they could support about, or more, 0.5-0.8 MPa.

•

However, some foundations typologies are recurrent for high-rise buildings design, including: pile, combined piledraft and slab and increased stiffness box foundations (Ukhov, 2003). Figure 1.17: “Space truss” system example: Bank of China, 1989, Hong Kong Source: (cc-by-3.0) WiNG

In order to select a suitable foundation system for a tall building, several factors © Council on Tall Buildings and Urban Habitat

Shallow foundations: These transfer loads to the earth just below the base of the substructure’s column or wall. Among them, mat and spread footings (isolated footings such as column footings, strip footings such as wall footings and combined footings) are considered the most common. These foundations are suitable for sites where soil conditions are adequate, since highly concentrated and eccentric column loads require a large foundation thickness.


•

Deep foundations: They transfer the load to a point far below the substructure. They are suitable where loads must be transferred in layers located below the ground surface due to the lower load bearing capacities of the soil near the surface.

The most common types of deep foundations are piles and caissons, as described below: •

•

Piles: These behave like columns embedded in the ground and transfer the load to a lower level of the subsoil. A wide variety of materials and installation processes are used in the piles. They can be classified based on the technology used in their construction. Nondisplacement piles are those in which a column of soil is removed and replaced with steel reinforcement and wet concrete. Displacement piles are driven in the soil, but they are losing popularity since the driving process causes noise, vibration, and dust (Chew Yit Lin, 2001). This category includes precast reinforced concrete piles, steel H-piles, composite piles, etc. Based on the load resistance system used in each case, piles can be end bearing (when the load on the pile is transferred to the soil layer located at the head pile level) or friction (when the resistance is mainly provided by the adhesion or friction action of the soil around the perimeter). Caissons: They are shells or casings that, when filled with concrete, form a structure similar to a cast-in-place pile but larger in diameter. They allow the load to spread over an area large enough to meet the soil bearing capacity. Their lengths are set based on a distance in which a


satisfactory bearing stratum such as rock, dense sand, gravel, or firm clay can be reached. Caissons can vary, from the technologies adapted in them, to various types: bored caisson, gow caisson, socketed caisson, box caisson, and pneumatic caisson. Poulos (Poulos, 2011) highlights how the design of foundation systems for high-rise buildings involves particular requirements based on the cyclic nature of wind, earthquakes, and wave loadings; moreover, differential settlements, both within the high-rise footprint, and between high-rise and low-rise areas, should be controlled by the design.

Frankfurt, Germany used 0.5 m3 of concrete per m2 of building area, which comes out to 143 m3 of concrete per floor. In Shanghai Tower, a 632-meter supertall tower in China according to the data on CPRF material take offs provided by Si et al. (2012) and the building dimensions provided by CTBUH (128 floors, 420,000 m2), 0.24 m3 of concrete is used per m2 of building area, which comes out to 785 m3 of concrete per floor.

According to some authors (Poulos, 2011) (Quick, 2005), high-rise buildings are usually founded on some form of piled foundation which is exposed to a combination of vertical, lateral, and overturning forces. Particular attention is paid to the piles and especially Combined Pile-Raft-Foundation systems (CPRF), which are the predominant types used nowadays. In CPRF system, loads are transferred by the skin friction and end bearing of the piles as well as the contact pressures of the raft foundation (bearing pressure). While in most cases a raft foundation provides the required factor of safety by itself, serviceability might not be guaranteed. Therefore, piles are associated to a raft, creating a composite load bearing system that benefits from the control of settlements accomplished with piles that provide most of the stiffness at serviceability loads, with the additional capacity (at ultimate loading) provided by the raft. In order to give an approximation for the amount of concrete required in a CPRF system, a 77 meter tower situated in





2.0 Sustainability and Tall Buildings


2.0 Sustainability and Tall Buildings

Skyscrapers are often accused of being a non-sustainable building typology because they require a greater amount of energy to operate compared to a normal building, they require increased quantities of materials for their structures as a consequence of their height, and they involve a higher amount of embodied energy used to produce these materials. Indeed, tall buildings require more structural materials than lower buildings and they utilize additional features (such as elevators) that are not needed in shorter buildings. The environmental sustainability issues of tall buildings became evident in 19731974 when the first energy crisis caused a rise in oil and energy prices in western countries. During the years following 1974, extensive analyses were carried out in North American cities to determine the actual energy performances of tall office buildings (Stein, 1977), while technical innovations were introduced to decrease their overall energy consumption (mostly in the field of mechanical ventilation and internal illumination), thus creating a new generation of efficient tall buildings. Since then, tall buildings have undergone

“Sustainability has clearly become a major driver of change in tall building development...” 26 | Sustainability and Tall Buildings

Figure 2.1: Integrated wind turbine example: Bahrain World Trade Center, 2008, Manama Source: (cc-by-sa) Ayleen Gaspar

major transformations that have changed not only the energy needed for their daily operations, but their architectural appearance as well. Sustainability has clearly become a major driver of change in tall building development, and the integration of “green” solutions has resulted in a whole new family of towers (Yeang, 1996) that have inspired the introduction of a new vernacular for tall buildings (Wood, 2007) (Yeang, 1996). However, green architectural features have been used sporadically, and only a few tall

buildings with extensive use of “visible” sustainable principles exist today. This is mainly due to the increased construction and management costs associated with developing such buildings, which need to be addressed by drivers beyond basic design factors. In fact, most high performance buildings have been built using less visible – but nonetheless effective – measures, rather than bold, outstanding innovations with very high capital costs. Thanks to the use of modern curtain wall systems, the exploitation of natural ventilation, energy efficient


elevators, combined heat and power units, and intelligent building control systems (Ali & Armstrong, 2008), buildings consume far less energy than their 1970s predecessors (Oldfield, et al., 2009). With a decrease in the energy consumption of tall buildings, a new issue arose, requiring the renewed attention of building experts and professionals: life cycle thinking. In fact, buildings consume energy and cause emissions, not only during use, but throughout their entire lives. From material production, construction, and maintenance, to demolition and the recycling of building materials (or disposal into a landfill), they consume energy as well as emit gases and substances into the environment. All of these phases have an impact on the total life cycle performance of a tall building, and one should make sure that the benefits of an energy reduction strategy (such as the use of a double skin façade) are carefully studied, so as not to create bigger drawbacks for other environmental characteristics; for example, by augmenting the initial embodied energy that offsets the benefits created in daily energy consumption. 2.1 Energy Consumption of Tall Buildings The energy consumption of tall buildings evolved significantly over the past 100 years, reaching a maximum before the first energy crisis and then diminishing remarkably (Oldfield, et al., 2009). The theoretical limit of 90 kWh/m2 per year mentioned by Raman (Raman, 2001) excludes the presence of on-site energy generation. Thanks to the exploitation of renewable sources such as photovoltaic

Figure 2.2: Photovoltaic façade example: Palazzo Lombardia Building, 2011, Milan Source: Dario Trabucco

Figure 2.3: Integrated wind turbine example: Pearl River Tower, 2013, Guangzhou Source: Tansri Muliani

cells or wind turbines, tall buildings can be not only efficient in consuming energy, but also in producing it.

Only a few tall buildings with integrated wind turbines have been built; the Strata Tower in London, the Bahrain World Trade Center in Bahrain, and the Pearl River Tower in Guangzhou (see Figure 2.3) are probably the most relevant examples. Generally speaking, renewable energy production systems are not as effective as expected, and cause many drawbacks to the comfort of a tower’s inhabitants (noise, vibrations, etc.). These drawbacks prevent their full exploitation and require mitigation measures (Killa & Smith, 2008) in the use of such systems, which have to be carefully assessed from a life cycle perspective.

Photovoltaic panels are being installed on a number of tall building’s rooftops, such as the Euro Tower in Rome, or façades, as on the Palazzo Lombardia in Milan (see Figure 2.2), but their effect is limited to the surface of their external envelopes, which are quite limited when compared to the building’s usable floor area. Therefore, their energy production rate is small when compared to the high energy consumption of the whole building.


Sustainability and Tall Buildings | 27

Energy Consumption [kWh/m2 per year]

Temperate Climate [Sydney]

Tropical Climate [Singapore]

Boilers

5.5

2.9%

0.0

0.0%

Chillers

13.4

7.0%

56.9

23.8%

AHU Distribution Fans

16.0

8.4%

17.5

7.3%

Water pumps

6.8

3.6%

10.3

4.3%

Cooling Tower Fans and Condenser

4.8

2.5%

12.1

5.1%

Package Unit

1.6

0.8%

1.6

0.7%

Tenant Condenser

3.9

2.0%

3.9

1.6%

Auxiliary Ventilation Fans

6.2

3.3%

6.2

2.6%

Total Base Building HVAC

58.2

30.6%

108.5

45.3%

Common Area Lighting

7.4

3.9%

7.4

3.1%

Lifts

13.7

7.2%

13.7

5.7%

Domestic Hot Water

2.2

1.2%

1.1

0.5%

Diesel Generator Testing

1.3

0.7%

1.3

0.5%

Hydraulic and Fire Pumps

1.9

1.0%

1.9

0.8%

Miscellaneous Non-Tenant Loads

2.0

1.1%

2.0

0.8%

Total Base Building Energy use

86.7

45.6%

135.9

56.7%

Tenancy Lighting

34.3

18.0%

34.3

14.3%

Tenancy Receptacle Equipment

69.3

36.4%

69.3

28.9%

Total Building Energy

190.3

100.0%

239.5

100.0%

Table 2.1: The Energy Consumption of a 60-story Office Building in Both Temperate (Sydney) and Tropical (Singapore) Climates Source: Partridge, et al., 2012; updated by CTBUH

“Because of the relatively recent ‘introduction’ of the notion of Life Cycle Assessment... there are no comprehensive Life Cycle Assessments with real verified data for tall buildings.” 28 | Sustainability and Tall Buildings

Leung and Weismantle (Leung & Weismantle, 2008) analyze possible sources of sustainability for supertall buildings that are achievable thanks to their height. Their study indicates that the gains through such measures are not enough to justify pursuing height for the sole sake of sustainability. The ultimate goal of the above mentioned sustainability measures (and other energy efficiency or on-site production solutions) is to realize a Net Zero Energy Building (NZEB), which would establish a balance between what the building receives from the grid, and what it returns to the grid during peaks of on-site energy production. So far, all attempts at reaching the NZEB

Figure 2.3: 30 St. Mary Axe, 2004, London Source: Phil Oldfield

goal for tall buildings have failed, due to: the excessive costs of high-performing systems, a lack of confidence and familiarity with such technologies (Chambers, 2014), and external vetoes (Frechette & Gilchrist, 2008). Even if the objective of creating a Net Zero tall building was realized – although this possibility is still debated – it would be far from a real “Zero Energy Building” (where a balance is established between what a building consumes in its life cycle – thus including the production of materials and construction – and what the building feeds back into the grid). In fact, energy reduction measures always come with an energy cost that is difficult to offset by on-site production, even on a small, simply-constructed building, making


Source

Foraboschi et al. 2014

Assessment Method (see section 3)

Process Analysis

Embodied Energy Structural Frame [GJ/m2 GFA]

Building Height [story]

Total Embodied Carbon [kg CO2/m2 GFA] -

-

-

3.15

40

Steel Frame + Concrete Core

-

-

-

3.94

50

-

-

-

3.77

60

Concrete Frame

Embodied Carbon Structural Frame [kg CO2/m2 GFA]

Total Embodied Energy [GJ/m2 GFA]

Structural System

-

-

-

2.20

40

-

-

-

2.57

50

-

-

-

2.46

60

Kofoworola and Gheewala 2009

Process Analysis


-

-

6.80

5.30 *

38

Oldfield 2012

Process Analysis

Steel Diagrid

955

340

-

-

40

Trabucco 2011

Input/Output

Steel Frame

-

-

23.20

-

40

Trabucco 2012

Hybrid Analysis

Concrete Frame

-

-

15.70

4.23

40

Concrete Core + Composite Column

-

-

18.00

11.70

42


-

-

18.40

11.60

52

Treloar et al. 2001

Input/Output

* Data not explicitly indicated in the paper, extracted through interpretation.

Table 2.2: Previously published studies on the life cycle assessments of tall buildings Source: CTBUH

it an almost impossible task when it comes to buildings as complex as skyscrapers. The energy consumption of a 60-story office building in both temperate (Sydney) and tropical (Singapore) climates can be divided as described in Table 2.1 (Partridge, et al., 2012). Interestingly, the results of the mentioned study show that the design team is responsible only for a small share of the total energy consumed by the building. In fact, the tenants’ office equipment (PCs, printers, etc.) can be responsible for a large portion of a building’s total energy (approximately 30% of the energy consumed in an office building is used by this equipment). As most of the electricity used by such equipment is turned into heat, HVAC

energy is needed to control these excessive heat gains, both from the equipment and other internal sources (especially for towers in a tropical climate). A similar concept can be applied to the consumption of the lighting energy in the space, though the design team can play a more important role in this aspect by choosing proper orientation, building shape, façade system, and by taking advantage of the available daylight to prevent the unnecessary use of artificial lighting during the day. Only a few of the above mentioned aspects related to a building’s energy use are really connected with building height; lifts,

water pumps, and HVAC fans are among those few. Other aspects (heating and cooling, domestic hot water, etc.) are more connected with the location and size/area of the building rather than its shape. Even the carbon releases that are related to the energy mix on the grid can be reduced by choosing to install energy conversion systems (such as fuel cells) in the building that reduce the need to utilize grid energy. When heating is needed in the building, using the heat generated in the space by the conversion systems as a heating source can also help reduce the energy and carbon impact of a building.



2.2 Embodied Energy of Tall Buildings

consumption of 0.23 GJ/m2 per year. The building is entirely made of concrete, with a PVC lighting system on the floor slabs.

Because of the relatively recent “introduction” of the notion of Life Cycle Assessment, and as a consequence of the inherent complexity of tall buildings that makes the acquisition of the necessary data a challenging task, there are no comprehensive Life Cycle Assessments with real verified data for tall buildings. At the same time, a few studies have been published on the topic from a theoretical and academic perspective (see Table 2.2).

Kofoworola and Gheewala (Kofoworola & Gheewala, 2009), studied a 38-story building in Thailand and found an initial embodied energy of 6.8 GJ/m2 GFA and a 0.86 GJ/m2 annual energy consumption. The structure in this case is made of a reinforced concrete core and steel frame and structural materials represent 77.8% of the total embodied energy (corresponding to ca. 5.3 GJ/m2 GFA).

Oldfield (Oldfield, 2012) performed a Life Cycle Assessment for a 40-story office building in London (30 St. Mary Axe) and assessed the embodied carbon as 955 kg CO2/m2 of gross floor area (1,159 kg CO2Eq. including building maintenance over 50 years of life phase) while the building’s total energy consumption per year stands at 95 kWh/m2 of electricity and 120 kWh/ m2 of gas which equals to 74 kg CO2/m2 of gross floor area each year.

Another paper presents the embodied energy or embodied carbon studies of existing or theoretical tall buildings, without benchmarking them against the total energy consumption of the building over its whole life cycle. A study on five buildings with different heights (3, 7, 15, 42, and 52 floors above grade) was performed using an input-output approach (Treloar, et al., 2001).

Oldfield takes into account the anticipated reduction of CO2 intensity in the UK’s electricity mix, and the final CO2 emission during a 50-year life is 3.5 tons of CO2 per m2. However, if the CO2 content from the electricity production is kept at today’s value, the final carbon content would be 3.7 tons of CO2 per m2 of the gross area. The studied building has a steel diagrid structure and concrete is used only on the floor slabs. Trabucco (Trabucco, 2011) estimates the total embodied energy of the same building to be 23.2 GJ/m2 GFA and the energy consumption to be at 0.43 GJ/m2 per year. Another study by the same author (Trabucco, 2012) on a 160-meter-tall building in Milan presents an initial embodied energy of 15.7 GJ/m2 GFA (4.23 GJ/m2 for the main structural components) compared with an energy 30 | Sustainability and Tall Buildings





3.0 Life Cycle Assessment


3.0 Life Cycle Assessment

Developed during the 1990’s, Life Cycle Assessment (LCA) is a methodology aimed at assessing the environmental consequences of human actions, particularly the production of goods. In the past two decades, LCA analysis has become more and more popular in all disciplines, including architecture and engineering. Despite the fact that LCA has been used for thousands of research projects analyzing the environmental characteristics of materials, components, and even entire buildings, and is widely described in books and scientific publications, doubts and criticisms still exist in the scientific community about the effectiveness and accuracy of LCA methods in accounting for all environmental characteristics of buildings and the built environment (Lenzen, et al., 2004) (Zamagni, et al., 2008). There are three main methodologies found in literature for performing a LCA (Treloar, 1998):

“...Life Cycle Assessment (LCA) is a methodology aimed at assessing the environmental consequences of human actions, particularly the production of goods.” 34 | Life Cycle Assessment

1. Process-based LCA: In a process-based assessment, the process to be analyzed is divided into all of its sub-processes. The inputs and outputs of each sub-process are quantified and the process analysis is repeated on all of the inputs, tracing the processes back to a “cradle,” where raw materials are excavated or harvested. This method has several problems, most notably concerning the arbitrary process of defining the boundaries of the analyzed system (to decide which processes are to be included or excluded from the analysis) and the availability and reliability of information regarding upstream processes. It is also a very time consuming and complex method. On the other hand, the process-based analysis is notable for its specificity and precision when it comes to detailed product studies. 2. Input-output LCA: In input-output assessment, all production inputs are converted into economic factors using industry-aggregated data on economic interchanges. All of the infinite material and non-material upstream inputs are included in the analysis using a mathematic algorithm. This method has been adapted from the environmental analyses that emerged from the research developed by Nobel Laureate W. Leontief in the 1940s. The problem with this method is that it uses industrywide average data, and therefore is not specific to a single product, site, or country, and the production processes and technologies for the same product can be very different in different parts of the world. The positive aspect of this method lies in its ability to assess the seemingly infinite upstream processes with a quick, simple calculation method.

or on a process analysis. Such systems try to take advantage of the positive aspects of the two main methods by combining them to perform a quick, comprehensive, and detailed LCA analysis. Hybrid systems are still relatively under development but they seem to be very promising for the future (Zamagni, et al., 2008). For the purposes of this study, a processbased analysis was adopted, as described in the International Reference Life Cycle Data System Handbook (JRC, 2010), a handbook released by the European Union’s Joint Research Centre, Institute for Environment and Sustainability, to guide users through the steps described in more general terms by ISO Norm 14044:2006. 3.1 Explanation of ISO LCA ISO Norms 14040:2006 and 14044:2006 are the reference standard for the LCA. According to ISO 14040:2006 (see Figure 3.1), a LCA is composed of four phases: •

3. Hybrid LCA: Hybrid systems can either be based on an input/output analysis © Council on Tall Buildings and Urban Habitat

Goal and scope definition: the definition of a study goal indicates whether the analysis is meant to simply provide a data set for a process – thus a Life Cycle Inventory (LCI) is its main deliverable – or a complete LCA analysis in which the Life Cycle Inventory is interpreted and compared to similar results for other processes or goods. The goal definition also identifies the intended purpose of the study (i.e., comparison of similar products) and the target audience. In the scope definition, the subject of the analysis is identified and described in line with what was stated in the goal definition. This includes the identification of the system boundaries and the functional unit; the analysis on the consistency of the methods; assumptions and

data; and finally, the declaration of the results‘ reproducibility. •

•

•

Inventory analysis: during this phase, all inputs and outputs of the process are acquired and described in line with the goal and scope definitions. It is usually the most time-consuming phase of a LCA, as it requires collecting and measuring a large quantity of data, which often comes from external sources. It is from the accuracy and completeness of the LCI that a LCA study gains its quality. Impact assessment: The Life Cycle Impact Assessment (LCIA) is the phase in which all inputs and outputs to the process collected during the LCI phase, are converted into impact indicators. Impact indicators are the tools that measure the impact of an analyzed process on target categories such as human health, the natural environment, and natural resources. Interpretation of results: The interpretation of results is often the most interesting and “proactive” phase of a LCA, as it gives recommendations on how to improve a process or selects the better process when two processes are compared.

3.2 Definition of the Goal of the Study The intended application of this study is to inform the community of professionals and researchers specializing in tall buildings on the environmental performance of the most common structural systems (reinforced concrete, steel and composite structural alternatives) by providing the most accurate, up-to-date analysis on two key impact categories: Global Warming Potential (GWP) and Embodied Energy (EE). The limitations of this study are represented by the fact that only

Life Cycle Assessment Framework

Goal Definition

Scope Definition

Interpretation

Inventory Analysis

Impact Assessment

Figure 3.1: Life Cycle Assessment Framework from ISO 14040:2006 Source: CTBUH

two impact categories (GWP and EE) are considered here, while other impact categories may lead to different results. Similarly, the obtained results are influenced by the quality of the information used, both in terms of environmental data (i.e., the “quality” and representativeness of the environmental data contained in the international databases used in the study) and data completeness (for example, environmental data on the end-of-life of tall buildings simply doesn’t exist, and had to be collected specifically for this research). The studied scenarios are representative of the most common structural systems for buildings of the height here considered.

This research is a complete Life Cycle Assessment of structural systems for 60and 120-story buildings. The main reason to conduct this study is that there is a lack of reliable and comprehensive information on the environmental impacts of various structural systems and materials for tall buildings, as well as the impacts of the construction phase on such projects. Also, a comparison on the relative importance of selecting various structural materials and structural systems for a tall building is needed. The intended audience of this public study is the community of tall building experts involved in the


Life Cycle Assessment | 35

490 meters for the 120-story scenario), and are ideally located in Chicago, USA. Considerations are therefore valid only for the given environment and under the prescriptive characteristics detailed further on. However, considerations derived from the results of this study can be applied to buildings of different heights, shapes, and locations from the studied building, provided that the variables remain within reasonable limits of the parameters in this study. As mentioned above, the system being analyzed is the above grade structural system of a tall building. The results will be presented considering the whole structure of the buildings, which represents the functional unit for this study. The scope of this study consists of the identification of the most sustainable structural system for tall and supertall buildings through a Life Cycle Assessment. Two different impact categories considered for this study are Climate Change and Resource Depletion, with Global Warming Potential and Embodied Energy as their selected indicators. Figure 3.2: 300 North LaSalle, 2009, Chicago Source: Marshall Gerometta

ownership, development, design, planning, construction, operation, maintenance, and research of tall buildings. The study was commissioned and sponsored by ArcelorMittal, the world’s largest producer of structural steel profiles and reinforcing bars for concrete construction. 3.3 Scope Definition of this Study As stated in the goal definition, the intent of this study is to provide a preliminary evaluation of the different structural 36 | Life Cycle Assessment

choices for the construction of tall buildings. The main deliverable of this study is represented by a Comparative Assertion LCA Study, which will identify the most and least convenient structural scenarios for a tall building from an environmental point of view, so as to quantify the environmental impact of the relative sector in the building industry. The study evaluates only the above-grade structural system for tall buildings of a given shape that differ in terms of height (246 meters for the 60-story scenario and

Fay et al. (Fay, et al., 2000) define Embodied Energy (EE) as “the direct energy purchased to support the (production) process under consideration, plus the indirect energy embodied in the inputs to the process.” Global Warming Potential (GWP) is defined as “the ratio of the time-integrated radiative forcing from the instantaneous release of 1 kg of a trace substance relative to that of 1 kg of a reference gas” (Shine, et al., 2010), which corresponds the measure of how much heat a greenhouse gas traps in the atmosphere compared to the amount of heat trapped by a similar mass of carbon dioxide.


The system boundaries of the study are extended to the whole life of the building structure, from the production and transportation of materials to the building site, through the construction and use phase, and including the demolition of the building as well as the recycling potentialities of the various components.

tall building structures built today (Ali & Moon, 2007). The structural schemes and materials are combined to recreate realistic design options. All plausible combinations of structural schemes and materials are studied for the two different heights, even if, in some cases, the resulting design would not be a common choice for a real building.

The data used in the Life Cycle Inventory (LCI) has been collected with the highest level of accuracy within the time and budget constraints of the research. Water consumption is not considered as an indicator in the study, regardless of the quantity. A detailed description of the methodology used to acquire the relevant information and prepare the LCI is described in the following sections of this report. For the interpretation and analysis of the results, this study considers three different parameters in the structure of a tall building: •

•

•

Height: the impact of building height is assessed by comparing buildings of 60 and 120 floors. According to Fazlur Khan’s “premium for height,” a building twice the height of another will have more than twice the structural materials of the shorter building due to the exponential increase of the lateral forces acting on its structure (Kahn, 1969). Structural material: steel, reinforced concrete, and composite (steel and concrete) materials are considered in the study as the structural materials of a building. These represent the most commonly used materials for the structural components of a tall building today. Structural scheme: several structural alternatives are considered by the study, covering the diverse types of

The cut-off criteria, coming from the comparative scope of the main deliverables, were set after an initial LCI model was modeled with the software used in the research (GaBi 6.0). This has allowed for the contribution of each flow to be identified, in addition to setting the cut-off criteria. The cut-offs pertaining to each specific part of the analysis will be described in their specific sections. Even though it is difficult to set an accurate life span for structural systems, literature shows that a 100-year time frame is a reasonable life for such complex structures. Despite this, the research has evidenced a progressive reduction in the life span of buildings, including tall buildings. This aspect is more extensively described in the section of this study that covers the end-of-life of tall buildings. It is important to mention that the final results of the research will be normalized for life cycles of 50 and 100 years. This will make the results comparable to similar research efforts on the energy consumption of office buildings and with the internationally adopted energy classification systems. 3.4 Scenario Analysis and Identification of Functional Units The purpose of this research is to study the whole life cycle of tall building structures and to compare the environmental effects

caused by variations in height, structural material, and structural scheme. The initial idea was to use data derived from real buildings to assess the environmental impacts of the different variations. The data were collected from the design firms for a number of office buildings recently completed in downtown Chicago. This strategy proved to be unreliable, mainly because the number of variables included in the analysis would increase excessively, while other random facts (design, shape, soil conditions, exposure to winds, etc.) that are not considered in the study would have affected the results, making them impossible to compare with each other. To limit the analysis to the three factors studied in this research (height, structural material, and structural scheme), the comparison had to be made among very similar designs, so as to keep the other variable’s effects minimal. Therefore, a different strategy was adopted and the focus was

“The purpose of this research is to study... tall building structures and to compare the environmental effects caused by variations in height, structural material and structural scheme.”



switched from a real case study to a fictitious building prototype inspired by a real building, which represents the current building practice for producing tall office buildings: 300 North LaSalle in Chicago, a 239-meter, 59-story office building completed in 2009 (see Figure 3.2). The building has a rectangular floor plan and a net rentable area of approximately 120,000 m2. Its structural system consists of a central concrete core and external steel columns connected via outriggers. The floor system used in the building was a composite solution that consisted of concrete slabs on metal decking.

Having imposed the height, core takeup of the gross floor area, the floor plan aspect of 2:3 (like the shorter building), and the constant core to width ratio of 13.5 meters, a tower with a floor plan area of 75 by 50 meters was created (see Table 3.1).

With this in mind, two main categories of design scenarios were studied: the first category for a building of 246 meters in height (59 levels above grade), and the second category for a tower of 490 meters (119 levels above grade). The shorter design is directly inspired by a “simplified” geometry of the 300 North LaSalle building. The taller design was modeled by

“The inventories obtained for the same scenario by two different firms should not be compared to determine a more efficient design or a ‘better’ solution.” 38 | Life Cycle Assessment

scaling up the smaller scenario, keeping within realistic proportions, especially in terms of core-to-window depth: it was kept at 13.5 meters representing a standard value in North American modern office buildings (see Figure 3.3). A realistic core size was also defined based on similarly tall skyscrapers, resulting in a NRA/GFA ratio of 75% (Trabucco, 2008).

The 60-story tower has a floor plan of 60 by 40 meters including structural elements. An area of 35 by 13 meters in the lower 40 stories and of 16.5 by 13 meters in the upper portion is allocated for the core programming of vertical services, lifts, etc. Outriggers are designed at the 40th floor. Assuming three interior core cross walls below the outrigger level; the outer two cells drop off after the outrigger level, at 2/3 the tower height (40 stories). The 120-story tower has a floor plan of 75 by 50 meters including structural elements, and an area of 55 by 23 meters in the lower 40 stories and 33 by 23 meters in the upper 80 stories are allocated for the core programming of vertical services, lifts, etc. It is imagined that three interior core cross walls are located below the outrigger level; the outer two cells drop off after the first outrigger level, at 1/3 the tower height (40 stories). The core program reduces after the first service level (40th floor) with added columns. In both cases, floor-to-floor height is four meters tall, with the exception of the lobby (6 m), mechanical floors (8 m),

246 m scenarios

490 m scenarios

(60-story equivalent)

(120-story equivalent)

Built Floor Area

144000 m2

450000 m2

Floor Plan Dimensions

40 x 60 m

50 x 75 m

Tower Slenderness

6:1

10:1

Lease Span (core to window depth)

13.5 m

13.5 m

Floor-to-Floor Height

4m

4m

Lobby Height

6m

6m

Mechanical Floor Height

8m

8m

Parameter

Table 3.1: Data of the Case Studies Used for this Report Source: CTBUH

and core penetrations on each side of the core that must be inserted via 2.5- by 3-meter openings. The shorter design would represent a normal office building of medium height in most global cities, if it were to be built. Its construction is quite standard and doesn’t require any particular design feature. On the contrary, the taller design would become the fifth-tallest building in the world and would have approximately one and a half times the gross floor area of the Burj Khalifa, the world’s current tallest building. This design, though realistic, does not represent a standard building of its height category. A building of this size would have been treated with an iconic architectural approach (Abdelraq, Baker, & Chung, 2004) in order to obtain constructive advantages from an informed design (Weismantle, et al., 2007). Also, as in the case of other supertall buildings (Baker, et al., 2007), various means of structural optimization would have taken


23.00 50.00 23.00 50.00

33.00 75.00

16.50

Scenario 1a, 1b, 4a & 4b Concrete core with Steel frame

55.00 75.00 40.00

13.00

(a = Steel grade 345MPa b = Steel grade 450MPa)

Scenario 1c & 4c Concrete core & Composite frame

13.00

40.00

60.00

(Steel grade 345MPa)

490.00

35.00

Scenario 2a, 2b, 5a & 5b All Concrete structures 4.00 8.00

334.00

4.00

Scenario 3a, 3b, 6a & 6b Steel Diagrid

246.00

8.00

(a = with wide and shallow beams b = with narrow and deep beams)

Scenario 3c & 6c Composite Diagrid (Steel grade 345MPa)

4.00 6.00

4.00 6.00

17.00

170.00

(a = Steel grade 345 MPa b = Steel grade 450 MPa)

Figure 3.3: Configurations for the 60- and 120-Story Variations Source: CTBUH

Interior Structures (the central core acts as primary element to resist lateral loads) Exterior Structures (the exterior diagrid system acts as primary element to resist lateral loads)

246 m Scenario

490 m Scenario

Concrete Core with Steel Frame

Scenario 1a

Scenario 4a

Concrete Core with High Strength Steel Frame

Scenario 1b

Scenario 4b

Concrete Core with Composite Columns

Scenario 1c

Scenario 4c

Concrete Wide and Shallow Beams

Scenario 2a

Scenario 5a

Concrete Narrow and Deep Beams

Scenario 2b

Scenario 5b

Steel Diagrid

Scenario 3a

Scenario 6a

High Strength Steel Diagrid

Scenario 3b

Scenario 6b

Composite Diagrid

Scenario 3c

Scenario 6c

Table 3.2: Scenario Codes for the Case Studies Used for This Report Source: CTBUH

place (such as tapering, variations of its geometry to “confuse” the wind, use of tuned mass dampers, etc). As a result of this “boxy” and nonoptimized shape, the 490-meter-tall scenario might result in being oversized, from a structural perspective, when compared to real tall buildings of similar height. Bearing this in mind, it was decided to proceed with the study of these scenarios in order to assess the environmental impacts connected with increases in the height of the building. As previously mentioned, the results of this study will be refer to the building as a whole, representing the functional unit of this study. Environmental impacts “per net square meter” or “per floor” are not considered in this study, as buildings are often built to occupy the maximum volume



EN15978 System Boundary

(Hvac, Hot Water & Lighting)

Exported Energy

Recycling

Recovery

Reuse

C4: Disposal

C3: Waste Processing

C2: Transport

C1: De-construction / Demolition

B6: Operational Energy B7: Operational Water

Transport of Construction Labour

Benefits and Loads Beyond the Building Life Cycle (D)

End of Life (C1 – C4)

B5: Refurbishment

B4: Replacement

B3: Repair

B2: Maintenance

Use (B1 – B7)

B1: Use

A5: Construction & Installation

Construction Stage (A4 – A5)

A4: Transport

A3: Manufacturing

A2: Transport

A1: Raw Materials Extraction

Product Stage (A1 – A3)

Operational Energy

(All remaining energy used within the building)

Figure 3.4: EN15978 System Boundary Source: CTBUH

allowed by local codes, so the net usable area is typically a consequence, not an objective, of a building’s design. The study omits the occupancy phase of the building, and it is thus not applicable to a specific duration of use, as research evidence showed that the impact of the structural components during a building’s use phase was not measurable, and the environmental performance of the building is predominantly controlled by other aspects of the design (function, curtain wall performance, MEP systems, etc). 3.5 System Boundaries The system boundaries of the study (see Figure 3.4) are extended to the whole life of the building structure, from the production and transportation of materials to the building site, through the 40 | Life Cycle Assessment

construction and use phase (subsequently excluded from the results), the demolition of the building, and the recycling potentialities of the various components (presented as additional information since it is beyond the system boundaries set by European Norm 15978 “Sustainability of construction works – Assessment of environmental performance of buildings – Calculation method”) (European Norm, 15978:2011). 3.6 Structural Systems and Materials The scope of the analysis in this study also includes the assessment of the role that different structural materials and systems play in the Life Cycle Assessment of tall buildings. Even if virtually all combinations of materials and schemes are possible and all buildings somehow act as “unique” structures,

two main families can be identified: interior and exterior structural systems based on the location of the primary lateral load-resisting system (Ali & Moon, 2007). The 16 scenarios imagined for this study are defined, including all possible configurations: interior and exterior structures (see Table 3.2); steel, concrete, and composite constructions; and eventually, two different steel grades of 345 MPa (50 ksi) and 450 MPa (65 ksi); and four concrete grades between 30 MPa (4 ksi) and 70 MPa (10 ksi). 3.7 Floor Systems Used The floor systems adopted in this research represent the most common technologies used in tall steel or concrete buildings. The floor plate spans and programming of the study towers generally conform to structural bay depths that may be


considered for office programming. The information provided, though, is not exclusive to commercial office construction. The systems considered could equally be used for hotel, residential, and mixed-use towers. Users of this study will need to make informed decisions on the comparative use of its data, based upon the selection of floor framing systems and floor spans for their specific projects. Three different alternatives were imagined: one steel-concrete composite solution that was adopted on all structures with steel or composite columns, and two alternatives to be used only on the “allconcrete” scenarios. The composite floor system was defined based on a 7.5 cm corrugated metal deck with a 6.5 cm collaborative slab of concrete that embeds a welded wire fabric and additional reinforcing rebar (when required). Shear studs directly connect the concrete to the steel beams underneath, thus creating a composite floor system that represents the common floor system for tall buildings. Gravity beam quantities were not calculated by the design firms, who designed vertical structures. Instead, they were derived using average values from the real case study and as a reference for this research. The concrete towers were studied considering two different floor variations: one with narrow and deep concrete beams, and another with wide and shallow concrete beams. The narrow and deep design is made of a 15 cm-thick slab with 40 cm-wide and 45 cm-deep beams every three meters, while the wide and shallow floor scenario is based on a 22 cm-thick slab and band beams 45 cm-thick and 200 cmwide, aligned with the columns. 3.8 Inventory of Materials Methods for obtaining information in the Inventory of Materials are described below.

These topics are then covered at length in the sections that follow. Quantities of Materials The analyzed system is represented by the functional unit (i.e., the structural system) delivered by the construction company to the other contractors that will transform the structural skeleton for future use. It does not include secondary non-structural components of the building, such as the exterior envelope enclosure, partition systems, finishes, and MEP systems. Inputs to the analyzed system were modeled by attributing the material quantities to the supply-chain of the construction company, represented by the material suppliers and the transport companies that deliver the materials to the site. With the use phase being excluded for the above mentioned reasons, research considerations skip to the end-of-life scenario for a demolition company, whose “inputs” (energy) and “outputs” (emissions and debris) are quantified. Production of Materials All the above mentioned quantities were calculated thanks to the support of several industry leaders who voluntarily contributed to the research by modeling specific structural scenarios: Arup, Buro Happold, Halvorson & Partners, Magnusson Klemencic Associates, McNamara/Salvia, Nishkian Menninger, Severud Associates, Skidmore, Owings & Merrill, Thornton Tomasetti, Walter P Moore, Weidlinger Associates, and WSP USA. These structural engineering firms provided the structural material quantities on the basis of a document containing general design information for the scenarios, which itself was prepared with the support of Magnusson Klemencic Associates. The document contained a description of the analyzed structural systems, the schematic layout and section of the structure to be designed, details of the

floor systems (designed by Magnusson Klemencic Associates), as well as the structural loads to be considered for the design of the vertical structures. Each scenario was assigned to two engineering firms. The structural engineering firms contributing to this research were asked to design the buildings using their business experience, but were limited in terms of structural optimization (i.e., by adding tuned mass dampers). Consequently, the resulting inventories of materials are likely to be over-designed when compared to the inventories of equivalent tall buildings in the real world. Also, it is important to note that the inventories obtained for the same scenario by two different firms should not be compared to determine a more efficient design or a “better” solution. Eight different configurations for the vertical structure were identified for the 60-story tower, and eight for the 120-story variation (see Table 3.2). A total of 16 scenarios were thus identified, with each scenario submitted to two design firms, so as to obtain 32 “bills of materials” that represent the basis of information for the subsequent phases of this research. The resulting quantities were integrated with data on the horizontal structural elements (i.e., floor beams, floor slabs, etc.) obtained from a comparison with buildings of the same size, function, and scale to those considered for the research. This phase regards steps A1–A3 (from raw material extraction to manufacturing) as described by EN 15978. The results of this section, directly derived from participating engineering firms, are presented in Table 3.3. Especially for the taller scenarios, even within the rigid boundaries of the design document, significant differences existed in the solutions provided by contributing firms. Where there are no significant design variations, the LCA results from two engineering firms designing the same scenario will be presented as an average



Scenario Number

6 ksi Concrete [t]

4-5 ksi Concrete [t]

Steel Rebar [t]

Welded Wire Frame [t]

Steel Studs [t]

Metal Decking [t]

Steel Beams [t]

Steel Columns [t]

Steel Trusses [t]

Fireproofing Spray [t]

12,857

6,077

28,424

1,388

260

25

1,212

4,011

1,971

186

1,651

7,608

12,036

28,424

957

260

25

1,212

3,949

1,614

333

1,651

12,857

6,077

28,424

1,388

260

25

1,212

4,011

1,840

186

1,651

7,608

12,036

28,424

957

260

25

1,212

3,949

1,307

333

1,651

13,844

8,218

28,424

1,554

260

25

1,212

4,011

786

186

1,600

-

8,758

13,761

28,424

1,122

260

25

1,212

3,949

667

333

1,600

-

13,340

6,900

80,803

3,332

260

-

-

-

-

-

-

5.962

-

31,464

8,280

80,803

7,481

260

-

-

-

-

-

-

2b_SF 01

24.150

-

13,340

6,900

58,939

3,281

260

-

-

-

-

-

-

2b_SF 01

33.782

-

6,955

5,631

58,939

6,309

260

-

-

-

-

-

-

3a_SF 01

-

-

-

-

28,424

548

260

25

1,212

4,862

5,850

1,800

1,742

3a_SF 02

-

-

-

-

28,424

548

260

25

1,212

4,156

2,050

4,970

1,742

3b_SF 01

-

-

-

-

28,424

548

260

25

1,212

4,756

4,250

1,700

1,742

3b_SF 02

-

-

-

-

28,424

548

260

25

1,212

4,051

1,640

4,900

1,742

3c_SF 01

-

-

-

13,617

28,424

778

260

25

1,212

4,848

3,050

1,900

1.600

10 ksi Concrete [t]

9 ksi Concrete [t]

8 ksi Concrete [t]

1a_SF 01

11.944

-

1a_SF 02

-

-

1b_SF 01

11.944

-

1b_SF 02

-

-

Concrete Core and Composite Frame

1c_SF 01

13.032

-

1c_SF 02

-

All Concrete Wide and Shallow Beams

2a_SF 01

24.150

2a_SF 02

All Concrete Narrow and Deep Beams

Short Description

Normal Steel + Concrete Core High Strength + Concrete Core

All Steel Diagrid Normal Steel All Steel Diagrid HS Steel

(SF = Structural Firm)

Composite Diagrid

Normal Steel + Concrete Core High Strength + Concrete Core Concrete Core and Composite Frame All Concrete Wide and Shallow Beams All Concrete, Narrow and Deep Beams All Steel Diagrid Normal Steel All Steel Diagrid HS Steel

3c_SF 02

6.049

-

5,221

3,243

28,424

1,188

260

25

1,212

4,236

610

1,490

1.600

4a_SF 01

76.864

-

23,242

64,209

83,543

7,424

764

75

3,563

11,861

25,923

2,641

4,844

4a_SF 02

144,744

-

29,938

-

83,543

10,683

764

75

3,563

11,608

19,369

5,125

4,844

4b_SF 01

76,864

-

23,242

64,209

83,543

7,424

764

75

3,563

11,861

25,923

2,641

4,844

4b_SF 02

144,744

-

29,938

-

83,543

10,683

764

75

3,563

11,608

16,420

5,125

4,844

4c_SF 01

85,130

-

32,563

81,793

83,543

8,028

764

75

3,563

11,861

5,526

2,641

4,702

4c_SF 02

179,399

-

38,511

-

83,543

10,560

764

75

3,563

11,608

3,538

4,990

4,702

5a_SF 01

104,871

-

65,368

40,242

237,496

17,064

764

-

-

-

-

-

-

5a_SF 02

139,518

-

82,184

49,981

237,496

20,399

764

-

-

-

-

-

-

5b_SF 01

104,871

-

65,368

40,242

173,232

16,915

764

-

-

-

-

-

-

5b_SF 02

139,518

-

82,184

49,981

173,232

21,330

764

-

-

-

-

-

-

6a_SF 01

-

-

-

-

83,543

1,611

764

75

3,563

18,062

14,850

54,900

5,284

6a_SF 02

116,667

71,029

41,765

-

83,543

9,991

764

75

3,563

11,147

784

29,719

5,166

6b_SF 01

-

-

-

-

83,543

1,611

764

75

3,563

18,062

11,700

54,900

5,284

6b_SF 02

116,667

71,029

41,765

-

83,543

9,991

764

75

3,563

11,147

784

29,719

5,166

6c_SF 01

56,925

-

31,050

37,261

83,543

7,911

764

75

3,563

18,062

-

8,550

4,702

6c_SF 02

55,306

24,724

17,281

32,799

83,543

5,620

764

75

3,563

10,952

648

21,138

4,702

Composite Diagrid

Table 3.3: Inventory of Materials Calculated Through the Research Project Source: CTBUH

42 | Life Cycle Assessment


value. In other cases, the two variations will be presented as two different alternatives for the same basic design scheme. For example, Buro Happold decided that a concrete core was needed in all of the diagrid systems for scenarios 6a, 6b, and 6c, while SOM felt it necessary to add concrete shear walls only on scenario 6c to meet the design criteria. Clearly, these choices have an impact on the inventories of materials and, consequently, on the LCA of the buildings. In the real world, these possibilities (and many more different design alternatives) would have been assessed for the design of a building structure, taking a greater number of variables into account such as cost of labor and materials, project timeline, contractor’s expertise, local and time-sensitive variables, etc. The resulting inventories of materials are presented in Section 9. Construction Process and Transportation Phase The transportation phase was modeled on the basis of the real material transportation distances for the construction of a tall office building completed in 2009 in Downtown Chicago, for which the engineering firm responsible for the comparative real building was able to provide a comprehensive set of information. The foundation systems associated with each of the considered tall building structures are highly relevant, but they are also very site-specific. Given the geographic variability of tall building projects, analyzing foundation systems were found to disproportionately skew the data sets in this study. Full LCA’s should include such considerations, but they have intentionally been omitted from this study to allow for a better comparative understanding.

Data for the on-site operations was calculated by contacting the suppliers of the largest machines operating on the comparative building site during the erection of the structures (cranes and concrete pumps) to receive information on their energy consumption. This phase regards steps A4 and A5 as described by EN 15978. End of Life The end-of-life quantities were obtained by consulting with three large demolition contractors operating on an international scale. Only the 60-story scenario was used in this circumstance as the demolition of such a building would still significantly exceed any previously demolished tall building. The same documentation that was provided to the engineering firms for the creation of the “bills of materials” was provided to the demolition firms in order to gather information on how a demolition project on this scale would be handled, which kind of machinery would be involved, and how long the demolition job would take. The responses of the consulted demolition contractors informed the creation of an end-of-life scenario for the various scenarios of the building structures. The demolition materials are considered to be hauled to the closest scrapyard and concrete recycling plant to the building site. This phase regards steps C1–C3 as described by EN 15978.




4.0 Steel: Cradle to Grave


4.0 Steel: Cradle to Grave

spans, and relatively small profile (which results in more space efficiency) are the qualities that gave rise to the popularity of structural steel products.

Steel is a highly demanded product used for many purposes, including buildings and automobiles. The use of steel as a structural element in buildings goes back to the mid-18th century, when the industrialized production of steel was made possible. It is a metal product with the unique ability to withstand both compression and tension forces, making it a great candidate for building structures.

carbonated to make steel. The steel is then molded and rolled into the desired shape (Yellishetty, et al., 2011). There are only a few integrated BOF mills in the United States that are able to produce large amounts of high-grade steel, a material mainly used in big steel profiles such as large structural steel sections and sophisticated steel products such as high-strength steel or alloy steel.

4.1 Steel Production Steel is produced using a complicated and energy-intensive process: it is produced through the carbonation of iron (pig iron or cast iron made of iron ore). This initial production procedure is done in blast oxygen furnaces (Yellishetty, et al., 2011).

As the construction of tall buildings became a trend in the 20th century, steel framed structures have become very popular. Their light weight in comparison to concrete or masonry structures, their capability of holding large forces (both horizontal and vertical) over wide

As steel is a highly recyclable material, a significant part of the new steel produced in the industry, especially in Europe and North America, is made out of recycled steel scrap. This production method utilizes Electric Arc Furnaces (EAF). Unlike

A Blast Oxygen Furnace (BOF) uses iron ore, oxygen blast, and coke, heating the compounds to make pig iron (see Figure 4.1). The produced iron pellets then get

GAS CLEANING

Raw BFG N2 CO2 NO2

FLUE DUST

Fe, C, S

150°C COLD BLAST

EMISSIONS

CO2, SO2, NOX

STOVES 1/3 BURN

HOT BLAST

AIR TURBINE AIR TURBINE

Figure 4.1: Schematic of a Blast Oxygen Furnace Source: Yellishetti et al, 2011, redrawn by CTBUH


COKE OVEN

1035 kPa STEAM

AIR TURBINE

CONDENSERS

COLD BLAST AIR HEAT OF COMPRESSION 150°C

FUEL

O2

IRON (Fe, C, S)

EFFICIENCY 80%

TO SINTER PLANT

46 | Steel: Cradle to Grave

STEAM 3100 kPa 400°C

BOILERS

COMBUSTION AIR

WIND SLAG (Ca, S, F)

PARTICULATE (NO2)

(C, Fe) Cast House Emissions Control

BFG (exported)

COLD STEAM ELSEWHERE

FEED WATER

STOCK HOUSE

PARTICULATE EMISSION

IRON ORE COKE LIMESTONE DOLOMITE

EMISSIONS

ELECTRICITY

CO2, H2O, NOX

CENTRAL BOILER STATION

BLOWING ENGINE

blast oxygen furnaces, EAFs use electrical energy to melt steel scrap and form the molten steel back into various shapes though molding and rolling (Yellishetty, et al., 2011) (see Figure 4.2). In 2014, 60% of steel in the EU was produced with the BOF method, while the remainder came from EAFs. In the US, the above mentioned percentages were inverted, with 40% coming from BOFs, and 60% from EAFs (WorldSteel, 2014).

FLARED STACK CO2 EMISSIONS

EMISSION CONTROL particulate

HOT IRON SCRAP DOLOMITE BURNT LIME FLUORSPAR

GAS ANALYSIS IN HOOD (circa 80% CO) INFILTRATION O2, N2

STEAM

Although the BOF method uses mostly virgin iron and the EAF method uses mostly scrap as the raw material, there is still scrap used in the BOF steelmaking process (about 25% scrap is used in BOF furnaces) and some virgin iron is needed in EAFs (5% virgin iron on average). The steel made in combination mills, which use a combination of EAFs and BOFs, thus contain an average amount of steel scrap based on the proportion of each production route in the overall number of steel products (Briggs, et al., 2010). Production data for steel typically utilizes an average of these routes, on both national and international levels.

ELECTRICITY

O2

Fe C

Fe

95% CO

Fe

C

C

C Fe

LIQUID STEEL SLAG

Figure 4.2: Schematic of an Electric Arc Furnace Source: Yellishetti et al, 2011, redrawn by CTBUH

The steel products from EAF mills are usually smaller in size and sometimes lower in grade compared to the steel from integrated BOF mills. Steel rebar and other reinforcement steel products are mostly produced using the EAF method and thus contain significant scrap content, while structural steel sections are produced using both EAF and BOF routes (Yellishetty, et al., 2011). The actual scrap ratio of various steel products may differ based on the location of their source and, consequently, the environmental impacts associated with steel production can vary by production process. The coke-making and iron-making processes in a BOF mill contribute much more to the environmental impacts of steel than the electricity used in EAF mills (Briggs,

et al., 2010), although the impact of steel production in EAFs also vary based on the energy source used to generate the required electricity.

There are two grades of steel used in the tall building structures considered in this research; normal-strength (50 Ksi/345 MPa) and high-strength (65 Ksi/450 MPa).

Although most new steel mills use electricity as their power source instead of burning coal or natural gas (ATHENA Sustainable Materials Institute, 2002), the average carbon footprint (1.77 kg CO2/ kg average) and embodied energy (24.4 MJ/kg average) of steel products is on par with the average of the world’s combined production processes (Hammond & Jones, 2008).

Although normal-strength and highstrength steel are not very different in terms of embodied energy and CO2 emissions (Stroetmann, 2011), the use of high-strength steel in tall building structures helps reduce the environmental impacts of steel by using a smaller quantity of steel profiles. Although the high-strength steel used in steel structures is mostly limited to


Steel: Cradle to Grave | 47

vertical structural members (Stroetmann, 2011) due to the lack of stiffness in lighter, high-strength steel profiles (AISC, 2012), they can be widely used in composite structures, where concrete coverage provides the stiffness needed by the design criteria, especially for the vertical elements whose design is dominated by buckling forces (Trabucco, et al., 2014). 4.2 Structural Steel Profiles Structural steel sections are the main components in a steel structure. Made out of hot rolled steel and usually shaped into a wide flange profile (I- or H-shaped), steel profiles are made in a way that directs the material mass to where the forces are applied on the structure (see Figure 4.3). The load-bearing capacity of steel components is related to their size (web height and flange width in case

of bending) and material thickness (for both web and flanges in case of shear or buckling). In other words, similarsized steel profiles can have different thicknesses, and therefore different structural capabilities. Structural steel sections are produced using both blast furnaces and electricarc furnaces in medium- to large-scale steel mills. Using a higher grade of steel compared to steel rebar, structural steel can use either less or more recycled steel, depending on its source and production location. ATHENA (ATHENA Sustainable Materials Institute, 2002) assumes 76% scrap content for structural steel profiles, while EcoInvent uses a higher scrap content as the average European value (85%). As the EcoInvent values have been adopted by Worldsteel Association as examples for good steel production

practice, they were also used in this research study. The GWP value of 1.14 kg CO2/kg and an EE of 14.8 MJ/kg are therefore used for this research. Structural steel sections represent highvalue steel components with a very high recyclability of 95% (American Iron and Steel Institute, 2013). Easy to dismantle, easy to access steel sections are very easy to recycle, compared to the reinforcement steel, which is embedded in concrete. A description of the possible re-uses of large steel profiles is given in the section dedicated to the end-of-life for tall buildings, see Section 8. Considering the fact that these buildings are constructed with very large steel elements, the research team, based on the results of the demolitions inquiry (see Section 8), decided to increase the recycling rate of structural steel components to 99% instead than the above mentioned 95%, which represents the average American recycling rate. 4.3 Steel Plates Steel plates are thicker, stronger sheets of steel that are mainly used in stiffeners, connections, or as base plates in steel structures. The steel plate connections are cut into specific sizes/shapes and then welded to the corresponding steel sections in order to make structural members (mostly beams and trusses). This process is done in the fabrication workshop.

Figure 4.3: Example of steel profile Source: ArcelorMittal Group 48 | Steel: Cradle to Grave

Unlike steel sections and rebar, steel plate consists of a high amount of virgin material (only 11% scrap content according to EcoInvent), as it is typically a product of a BOF steel-making route with high environmental impacts (with a GWP of 2.46 kg CO2Eq. and an EE of 26.07 MJ/kg). ATHENA (ATHENA Sustainable Materials Institute, 2002) considers 36% of © Council on Tall Buildings and Urban Habitat

Material Production

CO2 [Kg]

Energy [MJ]

894,000

11,500,000

(% of Total)

59%

58%

Fabrication

277,000

3,640,000

(% of Total)

18%

18%

Erection

342,000

4,740,000

(% of Total)

23%

24%

Total

1,510,000

19,900,000

Table 4.1: Breakdown of the Various Stages of Steel Construction Source: (Guggemos, et al., 2010)

scrap content, resulting in lower GWP and EE figures (1.33 kg CO2Eq. and 24.71 MJ/ kg) for steel plates, while Hammond and Jones (Hammond & Jones, 2011) consider no scrap content, resulting in much higher GWP (3.27 kg CO2Eq.) and EE figures (45.4 MJ) for each kg of plates. Due to its thickness, steel plates can’t be cold rolled, but need to be hot rolled like steel sections and larger steel products, making them even more energy intensive. At the same time, the content of steel plates in a building structure is limited to connections and stiffeners, which are considered to be about 5% of the weight of steel beams and trusses.

Usually, fabrication shops are located at a steel mill and perform welding, drilling, and machine-work as well as apply coatings and primers in controlled, factory conditions. Approximately 5% of new scrap is a result of this procedure, which returns to the melting furnaces right away (Davis, et al., 2007). Therefore, there is virtually no transportation involved in this procedure. Steel components are then shipped to the job site using high-capacity transportation means, like trains and trucks. The GWP and EE of the fabrication process must be considered when calculating the total environmental impacts of steel elements after they have been delivered to the building site (see Table 4.1).

4.4 Steel Fabrication Steel sections, plates, and connections need to be fabricated to produce the correct steel components for a building structure. The fabrication process includes: cutting to size, welding, drilling, and coating – and has to be done according to each project’s drawings and specifications. The carbon emissions and embodied energies associated with steel fabrication is described in Section 4.8.

In this research, the various structural elements are considered with different levels of complexity: trusses are simple steel profiles; beams are fully fabricated products (through the addition of steel plates as described below); and columns are steel profiles fabricated without the addition of any plates. Consequently, the total GWP and EE of columns and beams are calculated as follows:

Total GWP or EE of Steel Elements = GWP or EE of Steel Production + GWP or EE of Steel Fabrication As the GWP and EE of all steel products are available through cradle-to-gate Life Cycle Inventories used by the LCA software, the GWP and EE associated with fabrication procedures were not immediately available and had to be found in literature. A study conducted by the American Institute of Steel Construction (AISC) in 2010 shows that fabricating 1 kg of structural steel would have an average GWP of 0.215 kg CO2Eq. (Ranging from 0.261 kg CO2Eq./ kg to 0.193 kg CO2Eq./kg) and an average primary EE of 2.82 MJ (ranging from 2.42 MJ/kg to 3.71 MJ/kg) (Weisenberger, 2010). A different study (Guggemos, et al., 2010) shows that the electricity used to fabricate 1 kg of structural steel in the same project was 0.75 MJ/kg of the final product, which would correspond to 2.23 MJ of primary embodied energy (also accounting for energy waste during the production and distribution of electricity). Among all fabrication procedures, shotblasting (surface treatment with the use of metal shots to clean the surface and maximize attachment to the coating) and welding are the most energy intensive, together consuming 92% of the total energy used by the fabrication shop (Guggemos, et al., 2010). ArcelorMittal, however, provided a report prepared by P. E. International, a third-party LCA firm, which indicated the electricity input per kg of steel produced equal to 0.15 MJ. This case-specific value has therefore been used for this research. Electricity inputs of 0.15 MJ (corresponding to an EE of 0.44 MJ and a GWP of 0.03 kg of CO2) are added to each kilogram of beams



Figure 4.4: Use of steel rebar for the construction of structural reinforced concrete elements Source: Dario Trabucco

and columns; consequently, steel beams are considered as per the following:

materials like wood or steel elements in building structures.

1 kg Steel Beams = 0.95 kg of Steel Profiles + 0.05 kg of Steel Plates + 0.15 MJ of Electricity

Steel rebar is the lowest grade of steel products, produced locally almost everywhere using small scale electricarc mills (see Figure 4.4). It also has the highest content of recycled steel (containing 85% of recycled steel according to ATHENA and 69% according to Worldsteel) among all steel products used in the construction industry (ATHENA Sustainable Materials Institute, 2002) (WorldSteel Association, 2011).

Columns are considered as: 1 kg Steel Columns = 1 kg of Steel Profiles + 0.15 MJ of Electricity 4.5 Steel Rebar Steel reinforcement bar (rebar) are the “ribbed” steel rods used to reinforce concrete elements where the concrete is weak, in the places that tension, bending, or shear forces are at work. The reinforced concrete can be used to build structural members such as beams, columns, and shear walls, replacing other structural 50 | Steel: Cradle to Grave

Thanks to the high content of steel scrap, rebar have a GWP of 1.24 kg CO2Eq./kg and an EE of 16.42 MJ/kg according to WorldSteel. However better values can be found in the literature, such as the 0.45 kg CO2Eq./kg on Inventory of Carbon and Energy ( Hammond & Jones 2011).

Unlike structural steel, rebar and other reinforcement products are usually fabricated to the required form in a different location than the original steel mill. This adds a transportation factor to be considered when making comparisons in the LCA study (Guggemos, et al., 2010). The actual transportation means and distances, including those for the reinforcing steel, were calculated for this research based on what was used for the buildings that served as a reference. On the other hand, studies done on the end-of-life procedures at a leading concrete recycling facility near Chicago for reinforced concrete reveals that the reinforcements removed from crushed concrete members have concrete remainders attached to them (between 10% to 25% of weight), which makes them a lower grade of scrap and less


desirable materials for recycling and re-melting in steel mills (Guggemos, et al., 2010). This would decrease the recyclability of steel rebar to only 70% compared to structural steel, of which 99% can be easily used as scrap (American Iron and Steel Institute, 2013). This is mainly because of concrete particles that remain attached to the rebar even after crushing the reinforced concrete pieces and separating the rebar from the concrete. The concrete particles need to be taken off by hand, which makes the rebar more expensive to recover, and therefore, less desirable for scrap dealers. At the same time, concrete recyclers confirm that around 5% of the total reinforcements used in the reinforced concrete remains in the crushed concrete pieces.

according to Hammond and Jones (Hammond & Jones, 2008). However in most countries WWF is made from steel rebar, thus sharing the same environmental property of this highlyrecycled material. Considering that there is no cradle-to-gate process for WWF as a standard product in the current LCA databases, an alternative gate-to-gate procedure for WWF was created for this research to be used in the LCA procedure plans. The necessary information for creating the gate-to-gate LCA procedures were acquired by Schnell, a manufacturer of the machines used to produce WWF that shared with the research team the average inputs for a certain production of WWF.

The energy, materials, and parts used for producing WWF were calculated based on the specifications of the machine used for its manufacturing, while transportation factors were calculated based on the figures used from the manufacturer’s locations and transportation distances for the building that served as the reference for this research. The results show that the production process for 1 kg of WWF would have a global warming potential (GWP) of 1.25 kg CO2Eq. and an embodied energy (EE) of 16.57 MJ. Looking at the GWP and EE results for production of 1 kg of WWF, one can clearly see that the production of the steel wire rods keeps the highest share in both categories (99.3% of GWP and 98.3%

In the present study, however, a muchhigher recycling rate is considered. In fact, rebar used in tall buildings is thicker than those used in smaller buildings, thus making them easier and more profitable to be recovered. Consequently a recycling rate of 95% was used in this research. 4.6 Welded Wire Fabric Welded wire fabric (WWF), also called welded wire mesh (WWM), is a reinforcing steel mesh used in steel-concrete composite floors (see Figure 4.5). This material is commonly used in steel structures at large scales, including tall buildings. Although WWF works as the main tension resistance element in the floor construction, additional layers of rebar mesh can be added on top of it, based on the design criteria for lateral loads, or to improve the fire resistance of the assembly. Welded wire fabric is made of steel wire rod that contains almost 28% scrap according to Worldsteel Association (Worldsteel Association, 2011) and 42%

Figure 4.5: Welded wire fabric Source: (cc-by-sa) Frank Vincentz (Ies)



Process

Global Warming Potential [Kg CO2 Eq.]

Total

Embodied Energy [MJ]

1.25

100.0%

16.57

100.0%

Raw Material (steel rebar)

1.24

99.3%

16.42

98.3%

Electricity Grid Mix

0.013

0.6%

0.20

0.8%

Diesel Mix at Refinery

0.002

0.1%

0.20

0.9%

Table 4.3: GWP and EE for the Production of 1 Kg of Welded Wire Fabric Source: CTBUH

of EE). Table 4.3 shows the GWP and EE for the production of 1 kg of WWF. In order to verify the gate-to-gate process created for WWF, the results from the study were then compared with the results from similar studies in the literature. In the LCA of North American steel products conducted by ATHENA (ATHENA Sustainable Materials Institute, 2002), the total Embodied Energy for 1 kg of WWF is 15.24 MJ and the GWP is equal to 1.06 kg CO2Eq. In the Inventory of Carbon and Energy, Hammond and Jones (Hammond & Jones, 2008) consider 1.71 kg CO2Eq. as the GWP of the 1 kg of WWF, while the EE of its production would consume 24.6 MJ in their database. When the GWP and EE from the gateto-gate model developed for this study are compared to the above mentioned studies, the results show similarity to the LCA of North American steel products (ATHENA Sustainable Materials Institute, 2002), and remains in scale with the Inventory of Carbon and Energy results. Being a reinforcing steel element embedded deep into concrete floors and other components, WWF does not have a great recyclability potential. As with rebar, there is still 10% to 20% of concrete remainders on the element as well as a 5% steel remainder in the crushed concrete aggregates (as mentioned in Section 4.5). 4.7 Metal Decking In steel structures, steel decking is an important component of a composite steel-concrete floor. The steel decking 52 | Steel: Cradle to Grave

(made of corrugated steel sheets) holds all other components of the floor system together (steel reinforcements, WWF, and concrete slab), while also working to resist bending (see Figure 4.6). The advantage of the metal deck slab system is the elimination of formwork and shoring, and the consequent increase in construction speed. The metal deck can be used as a working and erection platform. Also, it acts as a diaphragm to help stabilize the steel skeleton by integrating all members into a system (Vinnakota, et al., 2003). Metal decking sheets are made from hotdip galvanized cold rolled metal sheets (with only 10% scrap content) (Worldsteel Association, 2011). The galvanized sheets are then bent and corrugated using electric powered hydraulic press machines and rollers, and finally cut into standard sheets. The scrap content, total GWP, and EE for producing the metal decking were also verified against the data from related studies. ATHENA considers 13% of scrap in the decking, resulting in the GWP of 1.76 kg CO2Eq. and EE of 27.66 MJ per 1 kg of decking sheets. Hammond and Jones, however, consider the decking made all out of virgin materials (no scrap content), yielding a GWP of 2.82 kg CO2Eq. and EE of 39 MJ for 1 kg of the final product. The Worldsteel data used in this research holds an average figure between ATHENA and Hammond’s results equal to a GWP of 2.56 kg CO2Eq. and an EE of 28.22 MJ per 1 kg. Like every other steel element, most of the energy consumption and carbon emissions for producing metal decks arises from the production of steel sheets

in the mill (ATHENA Sustainable Materials Institute, 2002). Although cold rolled steel is not considered a large steel product, the high content of virgin iron makes it an energy- and carbon-intensive product typically made in BOF steel mills. The thickness, span, and depth of the ribs in decking may vary based on the loading criteria of the project as well as the span of beams and above slabs (Vinnakota, et al., 2003). The steel deck alone has to withstand the weight of the wet concrete, plus any construction loads for the placement of concrete to achieve the desired non-shored condition, while the composite steel deck (steel deck + concrete) has to withstand the factored superimposed dead and live loads (Vinnakota, et al., 2003). As for commercial high-rise structures, the need for more net rentable office area and better daylight and view conditions in the space usually leads to longer spans, which need a deeper, thicker decking sheet (Vinnakota, et al., 2003). The metal deck, like other steel floor elements such as beams and joists, is connected to other floor elements via steel shear studs made from steel wire rods (28% from scrap according to Worldsteel). The size, number, and location of the studs depend on the design loads of the floor system as well as the criteria from structural design drawings and specifications. As an exposed steel element covering all floor slabs, metal decks are recycled fairly easily by detaching them from the slab during the structure’s demolition process. They are therefore considered with the same recycling rate of 99% which is used


Figure 4.6: Example of metal decking Source: (cc-by-sa) Kim Traynor

for structural steel scrap, shipped directly from the demolition site to the scrap yard together with structural steel sections. The steel shear studs, however, are to remain in the concrete slab and to be recovered later in the concrete recycling plant. 4.8 Steel Production Inventory Data As the credibility of a LCA analysis depends on the depth, accuracy, and comprehensiveness of the Life Cycle Inventory (LCI) it is based upon, the choice for the correct LCI that represents the most accurate datasets is a critical part of every LCA study.

Two of the main LCI databases used widely in LCAs on structural steel construction are the EcoInvent and Worldsteel databases, both of which are available (as complete cradle-to-gate datasets) for the software used in the research (GaBi V.6.0). These datasets are also available as pre-defined, detailed cradle-to-gate processes in the software library of materials. The characteristics of both mentioned data are described as follows:

• EcoInvent datasets: The EcoInvent

The cradle-to-gate LCI of each steel product needs to be assessed carefully from an ISO-complying, reliable database which is internationally recognized. The used “datasets” (LCI Processes) also need to best represent the region in which the study is done, following the most realistic routes for all components as well as the final product (Zygomalas & Baniotopoulos, 2013).

LCI database was initially developed in the late 1990s and contains more than 4,000 datasets referring to products, services, and processes. It was developed in Switzerland by the Swiss Centre for Life Cycle Inventories, which is also responsible for data updates. It refers to a mix of European technology, and the collection method used was a sampling procedure based on literature. A number of research centers in Switzerland and Germany


were involved with the development and constant update of the database, and the data are intended for use mainly within the European region (Zygomalas & Baniotopoulos, 2013). The EcoInvent database includes the dataset for steel manufacturing in an EAF route based on data from the year 2000, and also accounts for the transportation of scrap metal and other input materials to the EAF and casting. However, because this dataset refers to the manufacturing of steel up to the casting stage, it does not include the processes required for the production of hotrolled structural steel members such as the reheat furnace operation, the hot rolling process, and the transportation of the finished products to final storage locations before being sent out for use (Zygomalas & Baniotopoulos, 2013). The EcoInvent processes are marked with RER in the LCI databases.


• Worldsteel datasets: The Worldsteel

Association conducted an LCI study at a global scale in order to quantify all raw material, energy, and environmental emissions associated with producing steel products, including structural steel sections. The database was established in 1994–95, and was updated in 1999–2000 and 2010. The Worldsteel datasets provide cradle-to-gate (from raw material extraction to the steel factory gate) data on all the major raw materials. The study includes data on the energy usage, energy waste, air emissions, and water emissions of steel products. All environmental inputs and outputs are calculated for the production of 1 kg of steel products at the factory gate according to the ISO 14040 standard (Worldsteel Association, 2011). For structural steel, as an example, the data were collected from all over the world (but with very limited coverage of US mills). The mills from which the Worldsteel data were collected use some EAF steelmaking routes and some blast furnace routes. Therefore, the datasets use an average of both routes (Zygomalas & Baniotopoulos, 2013).

Another notable fact about the Worldsteel data is the credit for recycling. The scrap ratios and therefore the scrap credits are based on the global average ratio (80% for steel sections, for example), while the corresponding recycled content for steel in Europe and the US are much higher (the current US corresponding rate for structural steel is about 98% according to ATHENA) (ATHENA Sustainable Materials Institute, 2002). Looking at the two mentioned databases, the EcoInvent steel datasets miss some significant production processes (mainly reheating and the hot-rolling 54 | Steel: Cradle to Grave

process of steel), while data presented as Worldsteel “Global” datasets do not reflect commonly practiced steel production methods in the US market. This fact makes it difficult to use any of the predefined cradle-to-gate datasets that would best represent American produced steel, which is used in the studied scenarios for this research. The steel products included in the GaBi database (used in this research) do not include comprehensive cradle-to-gate data on American steel products yet. At the same time, creating replacement gate-to-gate processes for them can affect the consistency and accuracy of the whole LCA. Despite the fact that most of the structural and reinforcement steel products in the US are produced through an EAF route, while in their equivalent European products there is a higher share for BOF steel, the scrap content for European and American Steel is fairly similar. Additionally, the environmental regulations considered in American steel production is also more similar to European regulations than other parts of the world. This makes the European data a better replacement to the American cradle-to-gate datasets missing from the LCA software. At the same time, because the Worldsteel datasets are the most inclusive cradle-togate data on steel production – including almost all inputs, outputs, energies, and emissions – the best data for steel products used in the LCI come from Worldsteel. However, in recent versions of the software used in this research (GaBi V.60), the European average data presented in Ecoinvent datasets, is now adopted and completed by Worldsteel databases (Pe International, Inc., 2012). This new generation of processes can be used

as a replacement for US steel processes missing from the databases. Given these considerations, the cradle-togate datasets for all steel products used in this research are taken from the average European data (EcoInvent data adopted by Worldsteel) whenever available. Having a generally higher content of steel scrap (compared to the global average) in addition to generally lower environmental impacts, are the main reasons they are used in the research. 4.9 Life Phase Structural elements are considered permanent parts of a building through its life span, so there usually aren’t many changes, repairs, or replacements for steel structures, even if a building goes through a major retrofit or even a change of function. On the other hand, steel elements are subject to corrosion when exposed to the outside environment, yet most steel structure components are covered by a thick layer of fireproofing, coatings, and paint layers. This reduces the chance of corrosion and the need for replacement to a negligible level (Doering, et al., 2013). At the same time, the concept of “durability” in building structures has become broader than just the degradation of structural materials when sustainability aspects are taken into account. Canadian Architect (Canadian Architect, n.d.) proposes a new definition for durability that helps measure sustainability as the consideration of the durability like the equivalence between the useful service of a material (or component or system) and its time required for the absorption of its impact by the ecosystem. In other words, energy and resource-intensive structural materials need to have a very long service life to be considered durable, while structural materials mostly made


of natural materials do not need to live as long to be considered durable/sustainable (Buonopane, 2010). Structural steel, together with its alternative, is predicted to last throughout a building’s entire service life, which lasts between 75 and 100 years for tall buildings and is almost unlimited for supertall buildings (Buonopane, 2010). Therefore, structural steel is considered permanent and its environmental impacts minimal during the lifetime of a building. 4.10 Recycling As much as the concept of recycling steel members, such as beams and columns, sounds attractive from an environmental standpoint, liability issues, together with the need for thorough inspections and longer, more expensive dismantling procedures, keep the structural re-use of steel from finding a real market, especially when it comes to skyscrapers with large-scales and highly optimized designs.

Figure 4.7: Steel scrap yard Source: Dario Trabucco

structures have lower residual values because of the large amount of concrete Steel, in general, is a highly recyclable still attached to them after demolition material (95% according to American Iron and Steel Institute) (American Iron and Steel (Guggemos, et al., 2010). According to the Worldsteel association, there are two Institute, 2013) with a very high residual value ($385/T according to American Metal different methods for assessing the life Market and Scrap Price Bulletin). Most of the cycle of steel products: “closed loop” LCA and the “Credit/Burden methodology” revenue for both demolition contractors (Worldsteel Association, 2011). and recycling plants come from steel and other metal components that were once In the “closed loop” method, scrap used in a building. materials from the demolition/recycling process return to the beginning of the The high value and large market for steel production process, while the open recycled steel or scrap (Worldsteel credit/burden methodology focuses on Association, 2011), (Yellishetty, et al., 2011) the credit (negative figure in the final LCA in addition to the fact that steel keeps its results) that can be received from the characteristics after recycling, provide a scrap obtained from the demolition of the great advantage to steel structures versus concrete structures, which are heavier, more building structure. difficult to demolish, and can be recycled In this case, since the steel products used only to gravel for road construction. Even in the software datasets already use a high the steel reinforcements used in concrete

quantity of scrap as raw materials through the EAF production route (or combination routes including both BOFs and EAFs), the credit for scrap can only be awarded to the “net value of scrap” produced in the demolition process (Worldsteel Association, 2011). The net value of scrap is calculated by subtracting the steel scrap obtained from demolishing a certain steel product from the original quantity of scrap used to produce that product. Structural steel sections have higher EE and GWP than steel rebar, as they contain a higher grade of steel with higher level of virgin materials like iron ore (Worldsteel Association, 2011). As an example, to produce 1 kg of European steel sections, there is a need for 0.85 kg of steel scrap. The net scrap value for the average European data steel sections is calculated as follows:



calculated in order to assess the credit for scrap correctly. This average value will depend on the net scrap ratio for each steel product as well as the share of each product in the final scrap mix. This ratio also differs from building to building, depending on the types of steel products used in them. For instance, the scrap from a concrete structure is mainly made of steel rebar, while a steel building with a concrete core or an all-steel building can contain different amounts of steel sections, plates or decking which are more easily recycled. In order to obtain an average net scrap value for each design scenario, quantities of the different steel products in that scenario are calculated, while the scrap inputs for each steel product are taken from the LCI of each structural material. The net value of scrap for each steel product in the scenario are then calculated by subtracting the total scrap input for each product from the total quantity of that product in the building. The result from this equation is the total net scrap from that product.

Figure 4.8: Steel scrap yard Source: Dario Trabucco

“...The research results are presented under two different scenarios to denote end-of-life of the building...”

56 | Steel: Cradle to Grave

Net value of scrap for steel sections = 1 kg – 0.85 kg = 0.15 kg Out of the 1 kg of steel scrap created by the demolition of sections, 0.15 kg is the amount which can be used to “obtain” the credit, as the remaining fraction was already produced using steel scrap. The global warming potential and embodied energy for the production of different steel elements differ based on their manufacturing process and source. At the same time, the steel scrap coming from a demolition project is a mixture of all the different steel products used in the building. Therefore, an average net value for scrap has to be

As structural and reinforcement steel scraps have different recycling routes and different recycling factors, the total net scrap quantities for structural and reinforcement steels are calculated separately for each design alternative. These two numbers are then added to calculate the total net scrap quantity for that design. The net scrap ratio, for which the scrap credit is awarded, is then calculated by dividing the total net scrap quantity by the total steel used in the building. (Worldsteel Association, 2011). However, it is important to note that the scientific community of LCA practitioners does not unanimously accept the procedure suggested by Worldsteel. In


Figure 4.9: Separation of the different material waste Source: Dario Trabucco

particular, the fact that a benefit (i.e., the credit for scrap) is awarded now for something (i.e., the recycling of the material) that may or may not happen in the future is criticized. The “credit for scrap” principle is based on the assumption that the use of steel will grow indefinitely worldwide and, consequently, that the need for steel scrap will always exceed its availability. As a result, one can assume that the steel produced today will be recycled and, therefore will save both the raw materials and energy associated with the extraction, transportation, and production of steel from virgin iron. Despite this assumption – which is based on the current conditions of the steel market – if steel use should decrease in

the future, some of the steel used today will not be recycled as scrap and the environmental benefits accounted for by the credit would not be realized. For this reason, the research results are presented under two different scenarios to denote the end-of-life of the building: one where the energy for demolishing the building is considered, but no credit is awarded for the recycling of its materials, and another that includes “Module D” as described by EN 15978.




5.0 Concrete: Cradle to Grave


5.0 Concrete: Cradle to Grave

Various types of concrete are used in highrises: normal and lightweight (especially for floor systems); and conventional and high performance (with higher strength, durability, and workability). These are often integrated in the technologies adopted in tall buildings, which can vary from traditional Reinforced Concrete (RC) to post-tensioned systems that use highperformance concrete. Although in some recent studies (Weisenberger, 2010), where the benefits of structural steel frames have been demonstrated (reduced column sizes, high strength-to-member-size benefits), concrete systems have gained great acceptance and the material has been widely used by designers, especially since the 1970s. This is partially related to the fact that the concrete wall is the stiffest element currently in the structural engineer’s tool kit when conceiving tower framing systems. Tall building design is often controlled by stiffness more that strength. Also, concrete can be poured into different shapes, even under extreme weather conditions and temperatures, and is easily delivered to job sites (concrete plants tend to be conveniently located, even to city centers and busy metropolitan areas). Aggressive environmental conditions are countered with additives that are able to significantly enhance the durability of the material.

5.1 Cement Production and Transportation Cement consists of a controlled chemical combination of calcium oxides, silicon, aluminum, iron, and other ingredients. The most common manufacturing process for cement is a dry method. After quarrying raw materials including limestone, shells, and chalk (or marl), they are crushed in several stages using crushers and hammer mills. Crushed rock is then combined with other components such as shale, clay, slate, blast furnace slag, silica sand, and iron ore. The mixture is fed into a cylindrical steel rotary kiln that heats the ingredients to about 1480°C, powered by burning powdered coal, oil, alternative fuels, or gas under a forced draft. This heating and mixing process releases both clinker and gasses. Clinker (see Figure 5.1) is brought down to handling temperature in coolers. In order to increase burning efficiency and save fuel, heated air is returned to the kilns. The cooled clinker is

then mixed with small amounts of gypsum and limestone, then ground to a fine powder commonly known as cement. Among all concrete production procedures, cement production is responsible for the greatest amount of CO2 emissions: on average, every ton of cement produces 0.9 tons of CO2. Although cement industries have focused their efforts on reducing CO2 emissions related to the thermal energy of clinker production, little can be done to reduce the carbon released from limestone decomposition, unless the amount of Portland cement is minimized in the design mix. In fact, it is important to note in the equation below, CO2 is not released just as a consequence of the fossil fuels burnt to heat the mixture in the kiln, but also as a by-product of the chemical reaction that transforms the limestone in clinker, with the following percentages (Kestner, et al., 2010): 40% from the production of clinker;

As a consequence of the increase of concrete use, the environmental impact of concrete production is growing. Concrete production is considered to be responsible for up to 10% of global CO2 emissions (Ochsendorf, 2005), including infrastructure construction. Figure 5.1: Cement clinker Source: (cc-by-sa) Amit Kenny

60 | Concrete: Cradle to Grave


60% from the decomposition of limestone under high temperatures (above 1370°C). Simplified chemical reaction of cement production: CaCO3 + Heat → CaO + CO2 ↑ Considering that 15% to 20% of cement is used in conventional concrete mixes, replacing 50% of cement with fly ash or other substitutes can lead to a significant reduction in CO2 related to the “carbonation” of cement. A good concrete mix design is one that meets the required levels of workability, strength, and durability for every building. However, in order to meet more stringent sustainability requirements, the designer may consider using non-cement binders and recycled aggregates. The cement industry produces about 7% of global manmade CO2 emissions (Ochsendorf, 2005), of which 60% arises from the chemical process, and 40% from burning fuel. Emissions from cement production plants, apart from CO2, include dust, nitrogen oxide (NOx), sulphur oxide (SOx), as well as some micro-pollutants (World Business Council for Sustainable Development, 2002). Heavy metals (Tl, Cd, Hg, etc.) are often found as trace elements in common metal sulfides. Pyrite (FeS2), zinc blende (ZnS), and galena (PbS) are present as secondary minerals in most of the raw materials. In terms of energy consumption, cement production requires 4 GJ of energy per ton of clinker produced (Kestner, et al., 2010). Typical primary fuels used in clinker production are fossil fuels such as coal and petroleum cokes, as well as natural gas and oil. It is possible to use selected waste that meets strict specifications for combustion in a kiln, partially replacing fossil fuels. This waste often contains not

only recoverable calorific value, but also useful minerals such as calcium silica, alumina, and iron; therefore, it can be used as raw material in the kiln. However, the distinction between alternative fuels and alternative raw materials is not always clear, since some of them are characterized by both recoverable calorific value and useful minerals. Organic substances as well as alternative fuels can be used for this purpose, since the high temperatures of the kiln gasses destroy the toughest organic substances. Sustainability is not an empirical property of materials, since the choice of suitable materials cannot be based on numerical parameters, as is done in the process of selecting materials for their strength and elasticity characteristics. Therefore, in assessing the sustainability of building materials it is necessary to compare and quantify the environmental impacts as well as identify the context in which the material will be applied. Cement leaves the cement plant and is transported to either a distribution terminal or a final customer, such as a concrete production plant or a ready mix plant. Transportation and distribution occurs via boat, train, or truck. Cement transportation requires special care in order to avoid: contamination by residues or previous cargoes; solidification, if cement is exposed to humidity and wet conditions; and dust released during loading (dust can react with water and harden, damaging the transportation tools). Transportation by ship is particularly difficult: specialized ships called cement carriers are available with different capacities. More advanced technologies include cement carriers equipped with self discharging systems. As the commodity cost is quite low, transportation cost is a key factor in

competitively supplying customers with cement. 5.2 Cement Substitutes The American Concrete Institute’s Building Code Requirements for Structural Concrete (ACI318-11) defines a High Performance Concrete (HPC) as a special engineered concrete in which one or more specific characteristics have been enhanced through the selection of components. Thus, the concept of HPC has been evolving since the 1970s. For this reason Mehta (Mehta, 2004) suggests that the term “high performance” should be applied to the entire family of concrete mixtures that offer higher strength, higher durability, and higher workability. One of the engineered processes of HPC production is the partial substitution of Portland cements in mix

“...Cement substitutes ...reduce the carbon footprint, embodied energy, material waste in landfills, extraction of virgin materials and the environmental impacts related to manufacturing Portland cement clinker...”


Concrete: Cradle to Grave | 61

mix is considered as high-volume fly ash (HVFA) when fly ash comprises more than 50% of the mixture’s cementitious material by mass. Mehta (Metha, 2004) also suggests mixtures with low water (< 130 kg/m3) and cement content (< 200 kg/m3). Detailed requirements for superplasticizer use and slump tests are based on strength requirements.

Figure 5.2: Reinforced concrete core under construction Source: Dario Trabucco

design. Complementary Cement Materials (CCM) can partially replace cement and complement the hydration of cement products with a secondary reaction, forming a calcium silicate hydrate component. Fly ash (up to a 25% replacement in mass), slag (up to a 60% replacement in mass), and silica fumes (up to a 70% replacement in mass) are the most commonly used cement substitutes in concrete mixes. From an environmental standpoint, they reduce the carbon footprint, embodied energy, material waste in landfills, extraction of virgin materials, and the environmental impacts related to manufacturing Portland cement clinker, as they modify the chemical reaction happening in the kiln or during the hydration process. From a performance standpoint, they generally enhance workability, facilitate pumping, reduce bleed water, offer better resistance to segregation, and increase the durability of the final product. On the other hand, as these substitutes develop a lower hydration heat, they are characterized by a slower rate of strength gain. For this reason, they may 62 | Concrete: Cradle to Grave

be more suitable for use in the foundation and shear walls of high-rise structures, as these elements are not subject to high loads in the first few months of the project. Concrete mixes with cement substitutes may be not suitable for post tensioned slabs, where high strength is necessary in early stages. In order to achieve more sustainable results, Mehta (Metha, 2005) suggests the use of high-volume fly ash (HVFA), in which the replacement of cementitious material is greater than 50% in mass. Fly ash is a pozzolanic product of coal-fired power plants, defined in Cement and Concrete Terminology (ACI Committee 116) as “the finely divided residue resulting from the combustion of ground or powdered coal, which is transported from the firebox through the boiler by flue gases.” Class C fly ash – obtained by burning lignite or subbituminous coal - is the main type offered by ready mix suppliers for residential applications. High performance concrete (high strength, workability, and durability)

As the American Concrete Institute “Proportioning Concrete Mixtures Commission” (ACI 211) only provides specifications for concrete mixes with regular values of fly ash (up to 35%), but not the values found in HVFA, concrete producers only supply ready mixed designs for those mixtures. However, the procedure provided by ACI 211 offers solutions to design trivial batches of HVFA and also provides information on the adjustments needed in partially-cementreplaced concretes. The Committee is currently working on a report specifically on HVFA concrete (Bentz, et al., 2013). Some of the advantages of using HVFA concrete (Bentz, et al., 2013) are as follows: •

Reduced demand for water in the design mix (up to 20%): Using HVFA helps prevent cement flocculation by providing a desirable dispersion that reduces the amount of water required to achieve a given consistency. It also reduces friction and facilitates mobility, allowing it to act as a lowdensity void filler.

•

Improved workability: The mixtures using HVFA seem cohesive, easy to pump, and are less likely to segregate. A superplasticizer may be required for heavily reinforced applications.

•

Minimized cracks from drying shrinkage: Drying shrinkage is influenced by the amount of water in the mix, so reducing water


demand also helps reduce drying shrinkage cracking. •

Minimized thermal cracking: It has been proven that a 40 MPa concrete containing 350 kg/m3 of cement can raise curing temperatures by 55-60°C, resulting in a high cooling rate that can cause cracking. The same mixture with a 50% replacement of fly ash will only raise temperatures by 30-35°C, therefore reducing the possibility for thermal cracks.

•

Enhanced resistance to reinforcement corrosion, sulfate attack, and alkalisilica expansion: The durability of reinforced concrete components is affected by the permeability (especially by percolation) of the concrete through the interfacial micro-cracks close to aggregate surface. Fine particles of fly ash help to fill pores and reduce weaknesses in the concrete microstructure.

The process also consumes a large amount of fly ash, thus diverting it from landfill and reduces overall concrete quantities from achieving a higher-strength mix. Some of the disadvantages of using HVFA concrete are as follows: •

•

Longer setting time: The lower hydration rate of the fly ash creates a longer setting period. As chemical accelerators may be useful to improve the delays, the cost increase for using these substances can become prohibitive. Longer curing (moistening) time (longer than seven days): As fly ash hydrates slower than Portland cement, the water not consumed in the early-stage chemical reaction or absorbed by hydration may evaporate. Therefore, it is

Figure 5.3: Concrete floor slabs under construction Source: Dario Trabucco

fundamental to cure (moisten) the HVFA concrete for longer than the typical seven-day period. •

Higher tendency for plastic shrinkage cracking: HVFA concrete is harder than normal concrete and its mechanical behavior is similar to glass, with a higher fragility than normal concrete.

•

Slower strength development at early ages: In this case, in order to achieve acceptable early-age strength, it is possible to either reduce the water/ cement ratio, replace Type I with Type III cement (for a 10% cost increase), or add fine limestone.

There are examples where HVFA has been used instead of cement in concrete mixes for various projects in the US, most of which achieved positive results in terms of carbon emission reductions. HVFA with 50% cement replacement has been used in the US and Canada since 1987 for different applications such as slabs, beams, columns,

foundations, and finishing. Some examples of this, according to Mehta (2004), are the Hindu temple (2003) in Chicago (800 tons of CO2 saved), the Utah Capitol State Building seismic renovation (2006) in Salt Lake City (900 tons of CO2 saved), and the CITRIS Building (2007) at the University of California at Berkeley (1,950 tons of CO2 saved). From a life cycle perspective, the use of waste materials such as fly ash or silica fumes to replace cement in a concrete mix design allows for a significant reduction in the embodied carbon of concrete used in various buildings. According to the US Environmental Protection Agency (EPA), fly ash carbon emission is significantly low (0.011 kg of CO2 per kg of fly ash) compared to cement (0.95 kg of CO2 per kg of cement, data provided by ICE 2011) since fly ash is the byproduct of coal combusted for electricity generation. Also, no emissions are attributed to fly ash except those caused by its transportation. As far as durability is concerned, concrete is “durable” if it has achieved the desired



most of which pass through a 1 cm sieve. Coarse aggregates generally fall between 1 cm and 3.8 cm in diameter and are used in concrete in the form of gravels or crushed stones.

Figure 5.4: Steel reinforcement after the separation from concrete elements Source: Dario Trabucco

service life without excessive maintenance costs due to degradation or deterioration. ACI 201 “Guide to Durable Concrete” defines durability indicators as the behavior of the concrete with respect to: •

Freezing and thawing (including the effects of de-icing chemicals);

•

Aggressive chemical exposure (sulfate, seawater, acid, and carbonation);

•

Abrasion (floors, pavements, studded tires, and tire chains);

•

Corrosion of metals and other materials embedded in concrete;

•

Chemical reaction of aggregates (alkali-silica reaction and alkalicarbonate rock reaction).

more homogeneous, and the number of micro-cracks is reduced. More specifically, according to Bentz et al. (Bentz, et al., 2013), HVFA concrete provides significant reductions in Rapid Chloride Permeability Test (RCPT) values and corresponding increases in measured surface resistivity. It also shows increased resistance to deleterious expansion caused by AlkaliSilica Reactions (ASR) and a reduction in electrical conductivity (diffusivity). Despite the fact that cement substitutes are now becoming more popular, even in high-end applications such as tall buildings, the present research considers normal, commercially available concrete, as it still represents the most common choice in building sites around the world. 5.3 Gravel, Sand, and Aggregates

Research and tests on concrete made with cement replacements (Chan & Wu, 2000) demonstrate enhanced durability compared to concrete mixtures that use Ordinary Portland Cement (OPC). In concrete with cement substitutes, the porosity index is reduced, specimens have a good response to water permeability (if the cement replacements are accurately selected), composition appears to be 64 | Concrete: Cradle to Grave

Aggregates are inert granular materials (such as sand, gravel, or crushed stone) that constitute the bulk of a concrete mixture and account for 60% to 75% of its total volume. There are two types of aggregates used in concrete: fine and coarse. Fine aggregates consist of natural sand or crushed stone,

The total cost of surface mining dictates the technology used to extract aggregates (Smith, et al., 2001). The most commonly used procedure is simply called “quarrying” and the excavation methods depend on the type of deposit and its degree of consolidation. Highly consolidated rocks (or simply “hard rocks”) require drilling and blasting to reduce the mass to particle size (which can be dug from a loose pile). Primary fragmentation may be realized through explosions (using high explosives such as TNT-based dynamites or blasting agents such as ammonium nitrate solutions in a mixture of oil and wax) or ripping (mechanical breaking with a single tooth mounted at the rear of a powerful crawler tractor). If secondary fragmentation is required, it usually consists of secondary blasting, drop balling, or the use of hydraulic impact breakers. Under-consolidated or weakly-consolidated rocks can be directly extracted from the ground without these disaggregation procedures. There are various types of earth moving machines used for this purpose, among which the most common are hydraulic shovels and hydraulic backhoes. Particle sizes and shapes are obtained by crushing the extracted raw materials. Typical machines used for this purpose are the jaw, gyratory, and fixed blow-bar impactors powered by diesel engines. The jaw crusher compresses rock between a fixed jaw and a moving jaw to create breakage. The particle size is determined by the width of the aperture when the moving jar has fully retreated. Impactors are characterized by a chamber with a horizontal rotor revolving inside. The


rotor is fitted with either swing hammers or blow-bars. Comminution is achieved through the combined effects of the rock impacting against hammers or blow bars, inter-particulate collisions, and impact against the chamber lines (breaker plates). Typically, these systems are directly fed by quarried rock carried by dump trucks. More recently, the high cost of dump truck hauling has been an incentive to develop in-pit crushing systems mounted on fully mobile or semi-fixed frames. Hauling is a major cost factor in the production of construction aggregates, with considerable expenditures incurred in fuels, tires, and engine wear. Nowadays, most aggregates are moved by Heavy Goods Vehicles (HGVs), although air pollution and road traffic congestion may be reduced via freighting quarry products on rail or on inland waterways.

Figure 5.5: Concrete recycling Source: Dario Trabucco

developing compressive strength and much lower tensile strength.

Recycled aggregates coming from Construction and Demolition Waste (CDW) have a high potential to be used in concrete mixes (Silva, et al., 2014). The three main types of materials derived from CDW are crushed concrete, crushed masonry, and mixed demolition debris. If these materials are not reused, CDWs have to be placed in landfills or downcycled as ballasts for road and rail construction. Thormark (Thormark, 2001) suggests that the need for energy and natural resources can be reduced by recycling building waste, thus limiting the land area needed for landfill. 5.4 Concrete Production and Transportation Concrete production is a time-sensitive process consisting of mixing cement, water, and aggregates, sometimes adding chemical components called additives, to create a semi-fluid admixture which is poured into formworks to harden,

In general, concrete is a composite material and its performance depends on the amount and ratio of mixed components. During the concrete curing/ hydration process, the cementitious material reacts with water to create a cement paste that bonds the aggregates together until it hardens, obtaining a solid mass. The chemical reaction of hydration is presented below in standard notation: Ca3SiO5 + H2O → (CaO)•(SiO2)•(H2O)•(gel) + Ca(OH)2 Sand, natural gravels, and crushed stones are usually indicated as aggregates. A good design and redistribution of the aggregates in a concrete mix is achieved through vibration in order to avoid segregation, obtain a homogeneous mixture, and enhance durability. This is an issue, especially during concrete pouring and curing processes, since a strong and efficient covering for steel reinforcements must be maintained to prevent the penetration of water and moisture that causes uncontrolled steel corrosion or volume increase.

Additionally, chemical admixtures may be added to the concrete mix with different purposes: to speed up or slow down the hydration process (accelerators or retarders), entrain air bubbles (air entrainments), increase the workability of plastic concrete paste (plasticizers and super plasticizers), minimize the corrosion of steel reinforcements (corrosion inhibitors), improve pumpability (pumping aids), or color concrete paste (pigments). Other fine materials may also be added to the mix to improve concrete properties (durability, compressive strength, and workability) or as a replacement for Portland cement, such as fly-ash, blast furnace slag, and silica fumes. Concrete production may take place either in ready mix concrete plants, in which all components (except water) are mixed together, or central mix plants, where all components including water are mixed. The latter offers more control over concrete quality, but requires the plant to be close to the construction site, since the process of hydration begins immediately and concrete may harden during transportation.



EPDs of concrete

2,50

0,30

2,30

0,25 y = 0,0166x + 0,0739

Embodied Energy, MJ/kg

1,90

0,20

1,70

y = 0,0891x + 0,7826

0,15

1,50

1,30

Global Warming Potential, kgCO2e/kg

2,10

0,10

1,10

0,05

0,90 Embodied Energy GWP Projected Embodied Energy Projected Global Warming Potential 0,70

0

1

2

3

4

5

6

Compressive Strength, KSI

7

8

9

10

0,00

Figure 5.6: EPD Trends for Concrete Source: CTBUH

Once concrete is delivered to the job site by truck, it is poured into formworks and hardens, assuming the shape of the formwork it is poured into. The first few days after concrete pouring are essential to guarantee strength and prevent cracking. The curing process calls for controlling temperature and humidity conditions carefully; covering, spraying, or ponding concrete surfaces with water allows hydration chemical reactions to take place and prevents water evaporation. From an energy standpoint, little is spent on the concrete mixing process and the environmental characteristics of concrete are mainly determined by the ingredients of the mix, which will be analyzed separately in the following section. From a transportation perspective, 66 | Concrete: Cradle to Grave

concrete plants are nearly ubiquitous in developed regions, even in the proximity of metropolitan areas. Therefore, concrete has to travel shorter distances compared to other building materials. However, being a heavy material, its transportation requires many truck loads and the environmental impacts of this are significant. 5.5 Environmental Data for Concrete As shown in the inventory of materials for each scenario (see after the conclusions), the most common concrete used in the analyzed structural designs is “normal” C30/37 concrete. This concrete grade is being used for the creation of the composite floor system in steel-based scenarios, and to create the whole floor

assembly in all-concrete scenarios. For this material, environmental data are extensively available in the Ecoinvent database and the average values for European production are used for this research. On the contrary, no information is available for the higher-grade concretes being used for the vertical structures. The basic materials that constitute concrete, which were presented in the previous section, can be mixed in different proportions to create concretes with different properties. The “recipe” for these proportions is called the mixdesign. Depending on the desired characteristics of the final product (i.e., cost, strength, workability, resistance to chemical substances, etc.), the amount of each material can vary significantly (Bharatkumar, Narayanan, Raghuprasad, &


Ramachandramurthy, 2001). From a LCA perspective, this can have very important implications in terms of the Embodied Energy (EE) and Global Warming potential (GWP) of the final product. According to a study by the National Ready Mix Concrete Association (Nisbet, Marceau, & VanGeem, 2002), where an LCI of concrete products ranging between 20 and 70 MPa of compressive strength are presented, cement manufacturing represents the largest share of EE for the product, ranging between 69% and 84% of the total, with the highest shares corresponding to the highest concrete grades. The impacts of cement are even higher when CO2 emissions and GWP are considered, due to CO2 being releasing not just as a consequence of the energy used during its production, but also in the chemical reaction as limestone transforms into cement (see Section 5.1). For this reason, reductions in the amount of cement in the mix can have a major impact on its environmental properties (Khan & Siddique, 2011). For instance, the use of fly ash as a cement substitute can substitute a certain portion of cement (as much as 70%) with a by-product of other industrial processes (Dinakar, Kartik Reddy, & Sharma, 2013). However, cement substitutes may have an impact on other characteristics of concrete, such as curing time and hydration heat, so the appropriate mix should be selected according to each specific case (Alves, Cremonini, & Dal Molin, 2004). As a consequence of the variability in the ingredients that constitute a concrete mix, it has not been possible to identify environmental values for specific concrete mixes. As a consequence, average values for the concrete mix being used in the case studies have been identified by

Derived from BETIE

C30-37

Derived from EPDs

GWP [kgCO2Eq./kg]

EE [MJ/kg]

GWP [kgCO2Eq./kg]

EE [MJ/kg]

0.11

0.83

0.15

1.22

C40

0.15

1.12

0.17

1.28

C55

0.17

1.25

0.20

1.49

C70

0.16

1.23

0.24

1.67

Table 5.1: Environmental Values Used for the Different Concrete Grades, as derived from the online tool BETIE and from concrete EPDs in the San Francisco area Source: CTBUH

comparing over 1,400 Environmental Product Declarations (EPDs) from different concrete producers that operate in the San Francisco Area. These mixes present a great variability within each strength class, thus reinforcing the idea that a single value is unrepresentative of the many possibilities available. Also, no EPDs were available for concrete grades with a compressive strength above 50 MPa (7.5 kPSI); consequently, such environmental values were obtained with a linear projection of the GWP and EE contents of the lower concrete grades (see Figure 5.6).

concrete was obtained by averaging the values of 60 and 80 MPa concretes. Because of the silica fume contained in the concrete mix for the 80 MPa concrete, which is used to reduce the heat released by cement, the environmental data of the 70 MPa concrete is actually slightly better than the 55 MPa concrete, highlighting the variability of results across different concrete mixes.

In order to ensure the reliability of the results, and to show the major discrepancies that can arise with various design mixes from an environmental perspective, a second set of results was sought. This data was obtained from the French Syndacat National du Beton Pret a l’Emploi through the online BETIE (Beton et impacts environnementaux) tool (see Table 5.1). In this system, values existed for concrete with compressive strengths of 30, 40, 50, 60, and 80 MPa. Consequently, the environmental data of grade 55 concrete was obtained by averaging the values of 50 and 60 MPa concretes, while the data for 70 MPa

•

Different production systems: Small variations in the chemical composition of the raw materials can cause different emissions of CO2, especially during the chemical reaction that produces cement.

•

Different energy sources and energy mixes in the local power supply: A wide range of fuels can be used to produce the heat in a kiln. These can include natural gas or solid energy sources, including trash and used tires. Also, operations relying on electricity can have very different environmental impacts depending

By comparing the results of these two data sources for similar compressive strengths, major differences become evident. Such differences can be caused for a number of reasons. A non-comprehensive list includes:



even where it is still allowed, landfill taxes are applied per ton of disposed material, making concrete an extremely expensive material to discard. CDW recycling sites accept incoming concrete waste and transform it into recycled aggregates (RA) and other byproducts with market value. Fig. 5.7: Concrete recycling Source: Dario Trabucco

•

on the sources of the electricity supply in that area. Gas- or oilpowered plants, hydroelectric plants, and nuclear power plants all have varied carbon intensities per unit of distributed electricity.

environmental values for concrete are likely to be found for cements produced in less-developed economies.

Different efficiencies in the production process: Varied and obsolete technologies can drastically affect the efficiency of production operations.

Construction and Demolition Waste (CDW) represents a large share of the waste stream in most countries. It is responsible for about 32% of the 3 billion tons of total waste generated in Europe (European Environment Agency, 2010). It represents 154 million tons of waste in the US (Environmental Protection Agency, 2003) and 17.5% of China’s waste production (Urban Development Working Group, 2005). In Europe, concrete and other mineral debris represents the largest portion of CDW, though it varies by country due to the different construction techniques adopted. On the contrary, wood debris is the largest residential CDW in the US, while concrete is the more common material in non-residential CDW (Environmental Protection Agency, 2003). In Europe, CDW is recycled with varying percentages of efficiency, ranging from 98.1% in the Netherlands to 13.6% in Spain (Fischer & Tojo, 2011), but awareness of the problem is rapidly rising everywhere (Nitivattananon & Borongan, 2007). Landfilling of CDW is now forbidden in an increasing number of countries and,

5.6 Recycling of Concrete and Aggregates

Additionally, it should also be remembered that the accounting method used while compiling the Life Cycle Inventory of each specific product plays a major role in the precision of the final results because some of the operations may have been disregarded or overlooked when the information was collected. For this reason, the scenarios in this research were analyzed twice using both sets of environmental values. It is important to note that the environmental impacts represented here should not be considered as two ends of the spectrum in terms of efficiency. On the contrary, the fact that both values are derived from developed economies in areas with well developed environmental regulations (France and California) indicates that these represent good concrete production practices. Consequently, more negative 68 | Concrete: Cradle to Grave

Increasing the recycling percentages of CDW depends on the quality of debris and their on-site subdivision into different batches of homogeneous materials. Unlike low-rise residential projects, where a multitude of materials are used (Environmental Protection Agency, 2003), infrastructures and tall buildings are largely composed of two primary materials (reinforced concrete and steel) and economies of scale can be realized to facilitate an accurate sorting of debris from those representing smaller quantities, such as plaster, tiles, bricks, and carpets. Demolished concrete piles can either be processed on site, such as in the case of road construction (where crushed concrete is directly re-used as recycled aggregate), or transported to a processing facility for off-site crushing and sorting. Tall buildings tend to be located in dense urban environments and on-site crushing is typically prohibited due to noise and dust pollution. However, a certain degree of material sorting occurs during the demolition process, when large steel components (beams, corrugated sheets, etc.), aluminum, and other metals are separated from concrete for immediate recycling through the use of crushers and hydraulic shears mounted on robots and excavators. Different strategies exist to crush concrete blocks offsite. The first step usually consists of the primary crushing of blocks through an impact crusher that creates blocks approximately 80 mm in diameter. The output of the impact crusher is then


conveyed through a magnet that attracts steel reinforcements that once formed reinforced concrete. Crushed materials are then processed a second time, either with an impact crusher, rotary crusher, or through more innovative systems, explained below. This technique produces recycled aggregates that can be used as filling material after being washed. The finer dust produced is usually hauled to a land fill, though some alternative uses are being assessed. Transportation to the processing facility or landfill happens exclusively by truck and the distance travelled plays a fundamental role in the overall economic and energy balance of disposing/recycling crushed concrete (Marinkovic’, et al., 2010). Visits to Bluff City Materials, a CDW processor in the Chicago Area, showed that incoming loads (trailers or semi-trailers) are accepted free of charge if the demolition company hauls the material to the company’s main facility located 52 kilometers west of the city center, while Bluff City charges about $2.50 per ton if the material is hauled to their facility located 12 kilometers from the city center. Figures may vary if concrete is mixed with other CDW. If the quality of the incoming crushed concrete doesn’t meet specific requirements, the full load can be refused, as an excessive presence of other CDW can exceed the necessary levels of quality assurance for reuse, even as a road backfill material (Wahlstrom, et al., 2000). End-of-life concrete has always been viewed as a waste material with limited reuse possibilities because of the decreased quality of the product compared to natural aggregates (downcycling). Even after World War II, concrete and crushed masonry from bombed buildings were used as filling materials for the construction of road

beds, river banks, and other infrastructure. Such applications still represent the most common use of crushed concrete. In recent years, new possibilities have been investigated, predominately because of the excessive production of CDW in relation to the demand of filling materials. Among these, one of the most advanced programs is represented by the EU funded C2CA research (Advanced Technologies for the Production of Cement and Clean Aggregates from Construction and Demolition Waste - Grant Agreement n.265189), whose aim is to explore the possible uses of recycled aggregates from end-of-life concrete. According to the most advanced research in the field, innovative systems, including flow cavitation disintegration, high performance sonic impulses, thermalmechanical beneficiation, microwaves, and electric discharges can be used to weaken the cement paste that binds aggregates together in concrete, so as to obtain, through fine crushing, a better separation of aggregates from the cement paste (Menard, et al., 2013). The cement paste obtained with this method can be used as meal for the production of new cement clinker (Galbenis & Tsimas, 2006), while sand (Ulsen, et al., 2013) and aggregates can be used for the production of new concrete, both for non-structural (Soutsos, et al., 2011) and structural applications (Wagih, et al., 2013) even if the performance differences between concrete using natural or recycled aggregates are well debated in literature (Rao, et al., 2007). Tests have been carried out to assess the structural characteristics of highly “sustainable” concrete samples using a mix of recycled aggregates and fly ash cement, but results have not been satisfactory, with compression and tensile strengths being seriously compromised when substitution rates exceeded 30% of both aggregates and cement (Kim, et al., 2013).

Evidence shows that the environmental benefits of recycling concrete are limited and they can only be increased if broader system boundaries than those used in standard LCA analyses are included, particularly if social aspects and economic costs are included through a Life Cycle Sustainability Assessment (LCSA) (Hu, et al., 2013). Even in countries where the use of recycled aggregates is regulated, such as in Switzerland, cultural and economical barriers prevent a diffused use of recycled aggregates for high-profile applications (Knoeri, et al., 2011). However, natural resource depletion and land fill saturation are a growing concern in developed countries and increasing legislation will continue to promote research and development in this field. As for today’s research, the increased porosity and water absorption of recycled aggregates (Rao, et al., 2007) requires greater cement content (approximately 5% more) compared to natural aggregate concrete. Because of the large energy consumption and CO2 emissions of cement production (Hammond & Jones, 2008), the increased quantity of the bonding components shifts and annuls the environmental benefits of using recycled aggregate (Marinkovic’, et al., 2010). For this reason, and the purposes of this research, end-of-life concrete is supposed to be used as a recycled filling material only, and it is credited to the endof-life scenario accordingly. The recycling plant visited for this research requires, on average, 3.5 KWh and 0.7 liters of diesel per ton of recycled aggregate produced (only energy used on site). These values provide a combined energy consumption of 38 MJ per ton. This number is higher than those that the reference found in the literature, such as the 18.1 MJ/t calculated by Marinkovic’ (Marinkovic’, et al., 2010).




6.0 Fireproofing Materials: Cradle to Grave


6.0 Fireproofing Materials: Cradle to Grave

For steel, the process of losing strength starts at about 300°C and increases rapidly after 400°C. At 550°C, steel conserves only 60% of its characteristic yield strength. Usually, an unprotected steel section loses its load-bearing capacity within 30 minutes (BauForumStahl 2008) (see Figure 6.1). In steel design, the “section factor” is a parameter that relates the geometry of a section to the heating rate of the elements: Section Factor = Hp / A

72 | Fireproofing Materials: Cradle to Grave

Hp identifies the Heat perimeter of the steel section; A is the sectional area of the profile.

to use special coatings or claddings for steel structures and utilize concrete cover cases of appropriate size and thickness for RC structures (Tomasetti, et al., 2005) (Cowlard, et al., 2013) (see Table 6.1).

From this equation, it is clear that a massive section will heat up slower than a light, slender section. To avoid the risk of collapse due to fire, different passive fireproofing systems are used in steel construction. To ensure adequate fire safety and prevention, it is necessary

This research is aimed at comparing the environmental implications of different structural systems and solutions from a life cycle perspective. Consequently, the

Standard Fire Test BS476 Part20

High Temperature Steel Properties

1200

Room Temperature Strength Ratio

1.0 1000

Temperature °C

The fire resistance of a structure or a material is usually expressed by a number that represents, in units of time (minutes), their capacity to withstand the high temperatures of a fire before losing their mechanical characteristics. Concrete is not inherently susceptible to fire, but reinforced concrete can suffer serious problems if it is not adequately protected; in fact, the internal tensions generated by heat can cause spalling, a quick erosion of the thin concrete layer that protects the steel reinforcements. If the contained steel rebar is exposed to the heat generated by a fire, it will lose its strength capacity, thus causing a collapse of the entire reinforced concrete element. In general, a reinforced concrete structural element is selfprotecting against fire, simply because the layer of concrete that protects the steel rebar is thick enough to prevent exposure. Composite elements (formed by steel profiles encased in concrete elements) are completely self-protecting, as the layer of concrete encasing them is, for structural reasons, much thicker than what would be required for fire-protection purposes. Modern safety standards require the installation of auto-shutoff systems, but fireproof-treatment for structures must still be achieved in order to ensure appropriate fireproofing in case of an out-of-service sprinkler system.

800 600 400 200 0

20

40

60

80

0.8 0.6 0.4 0.2 0.0

100 120

0

200

400

Time (minutes)

600

800

1000

1200

1400

Temperature °C

Figure 6.1: Standard Time-Temperature Relationship for Fire Tests (Left) and Steel Strength Decreases with Temperature (Right) Source: CTBUH

Section Factor [Hp/A]

Cementitious Sprayed-On Materials Dry Thickness in mm to Provide Fire Resistance for up to: 0.5 h

1.0 h

1.5 h

2h

3h

4h

30

10

10

14

18

26

35

50

10

12

17

22

33

43

70

10

13

19

25

37

48

90

10

14

21

27

39

52

110

10

15

22

28

41

54

130

10

16

2

29

42

56

150

10

16

23

30

44

57

170

10

16

23

30

44

57

Notes: For castellated or cellular beams, or fabricated beams with holes, the thickness of the fire protection material should be 20% more than the thickness determined from the section factor of the original.

Table 6.1: Requested Thickness of Typical Spray Cementitious Fire Protection Material Source : ASFP Yellow-Book, 4th Edition 2012


different structural possibilities under analysis have to be comparable across a similar level of fire protection. For this reason, the environmental consequences of a fire-proofing layer are added to the steel components of steel structures in order to ensure comparable fire behavior with concrete and composite structures.

In terms of sustainability, during recent years, companies have developed “green” intumescent paints. In fact, in reference to ISO9001:2008, intumescent coating are water-based and include low Volatile Organic Compounds (VOC) formulations.

construction. Another advantage is the possibility of covering structural steelworks without the pre-treatment of steel surfaces. The required thickness of the boards depends on the location of steel sections, the number of fire exposed sides, and the fireproofing time request.

Non-reactive protective materials can be classified in three broad families: Boards, Sprayed mineral coatings, and concrete encasements.

In current international building code, the minimum required fire resistance has been changed from four hours to three hours (Gilsanz, 2008). For tall buildings in particular, the code requires that buildings must maintain their structural performance for a duration of three hours, ensuring not only the total evacuation of the building, but also an acceptable level of safety for the preliminary fire-brigade response that will extinguish the fire.

Sprayed mineral coating technology consists of a paste that is sprayed on a protected surface. The treatment of steel elements is usually not required, especially when the protective coating is based on Portland cement. Like IFRM, sprayed-on cement or mineral coating systems can be used to protect complex shapes. To ensure better adhesion and

The use of boards (plasterboards, gypsummade boards, etc.) is a non-reactive solution to protect steel elements from fire. This technology offers a cleaner solution as it represents a dry mode of

6.1 Types of Fireproofing Materials

Pro

Board

Passive fireproof materials (PFPM) can be divided in two families: non-reactive and reactive (see Table 6.2). Intumescent fire resistive material (IFRM) coatings are made from paints that are inert at low temperatures, but provide insulation as a result of a complex chemical reaction at temperatures of approximately 200-250°C (see Figure 6.2 and 6.4). Typical expansion ratios of an IFRM coating are about 50:1, so a 1 mm-thick coating will expand to about 50 mm. In order to ensure optimal fire-resistance efficiency, the thickness of the intumescent film is calculated based on the A/V ratio. In this way, optimizing structural steelwork to ensure the lightest elements may prove disadvantageous when considering the costs related to the application of intumescent paints. Thin film intumescent coatings can be applied on-site or off-site, and their main advantage is their capacity to cover complex shapes.

Non Reactive On-Site Application

Flexible/Blanket Systems

Reactive

Off-Site Application

Sprayed-On

Reactive

Cons

• • • •

Appearance Fixing Quality assured Surface preparation is not required

• • •

Cost Application Speed

• • • •

Cost Application Durability Surface preparation is not required

• •

Appearance Overspray needing

• •

Low cost Fixing

•

Appearance

• • • •

Cost Time requested Space utilization Weight

• • •

Cost Application Limited fireresistance period

•

DFT is dependent on the steel section used (Hp/A)

Concrete Encasement

•

Durability

Thin Film Intumescent Coatings

• • • •

Aesthetics Finish Application Servicing

•

Reduced construction time and relative costs Simplified installation Standard of finish, quality, and reliability Reduced on-site activities

Thin Film Intumescent Coatings

• • •

Table 6.2: Summary of Principal Fire Proof Technology Source: CTBUH


Fireproofing Materials: Cradle to Grave | 73

an adequate retention of the sprayed protective material, metal mesh made of galvanized steel is often used around larger structural elements. This solution is avoided whenever possible due to the high installation cost of such mesh. One of the oldest methods of increasing the fireproofing performance of steelworks is concrete encasement. Examples of this can be found in many tall buildings from the past, including Mies’s famous Seagram Building in New York (see Figure 6.3). Until the late 1970s, concrete was the most used material to ensure an adequate fire-resistance for steelworks. On one hand, this solution ensures high levels of durability, but on the other hand, it involves significant loads added to the building structure, provides inefficient space utilization, and elevates costs (compared to lightweight systems). Figure 6.2: One World Trade Center, 2014, New York City during construction, sprayed-on fire protection is used on all steel elements Source: Dario Trabucco

“...The most common fireproofing solutions adopted in tall buildings is the use of spray-on mineral coatings, which are capable of providing a cheap and reliable insulation...” 74 | Fireproofing Materials: Cradle to Grave

6.2 Environmental Impacts of Fireproofing Materials Research was conducted by reaching out to many international producers of fire-insulating materials. This yielded unsatisfactory results due to the fact that LCAs are not commonly performed by members of this industry. For intumescent paints, contacted companies use a “sustainable” label for water-based products that omit chemical solvents and for the reduction of volatile organic compounds (VOC) in their products. In general, technical datasheets provide a wealth of information about the performance of each product, but

Figure 6.3: Use of Concrete for Protecting the Steel Component in the Seagram Building, 1958, New York City Source: CTBUH


Figure 6.4: One World Trade Center, 2014, New York City during construction, sprayed-on fire protection is used on all steel elements Source: Dario Trabucco

unfortunately, values for embodied energy and embodied carbon are not available, except for plasterboard or gypsum-based materials. In the US, some gypsum-based plasterboard companies founded the “Gypsum Association” and, in February 2013, conducted a LCA study. The research found the GWP of 1 square foot of 1.25 cm and 1.60 cm plasterboard to be 233.3 and 315.4 kg CO2Eq. respectively. However, the most common fireproofing solutions adopted in tall buildings is the use of spray-on mineral coatings, which are capable of providing a cheap and reliable insulation that is applied on vertical and horizontal structural

elements soon after their installation in the building. Spray-on fireproofing material has been estimated as the sum of its basic components, so in the case considered, cement and polystyrene fibers. A specific LCA was then conducted on this paste and a GWP of 0.26 kg CO2Eq. and an EE of 4.37 MJ for each kg of paste was determined. The density of such compounds is approximately 240 kg/m3.

used for the fireproofing material in this research, which is applied with a 2.5 cm layer around vertical steel columns and the primary floor beams.

Grace, a fireproofing producer that operates in the US market communicated to the CTBUH that its products are being certified with a GWP of 0.22 kg CO2Eq. per kg and an EE of 2 MJ for each kg of sprayed-on concrete. The environmental information obtained by Grace have been


Fireproofing Materials: Cradle to Grave | 75


7.0 Transportation and On-Site Energy Use


7.0 Transportation and On-Site Energy Use

Transportation and on-site operations are often omitted from many analyses on the sustainability of buildings. This is due to the assumption that such operations play a marginal role in the environmental impact of buildings. Because of the unique factors involved in tall building projects, this research examines these impacts to confirm or deny this assumption. The complexity of the construction site has direct consequences on an environmental impact assessment. Unlike ordinary manufacturing industries, the products of the construction industry are always complex and unique, including a wide range of techniques and systems. Therefore, it is not possible to apply a globally recognized value for the environmental impact of each building (Gangolells, et al., 2011). The construction phase of a building is accounted for in stage “A5” of the LCA analysis scheme, according to the European Norm 15804, and it might play an important role in the total environmental impact of the building due to the necessary use of heavy equipment

(often diesel fueled), temporary and consumable material use, and waste generation (Guggemos & Horvath, 2006). 7.1 Transportation and On-Site Operations in Literature On-site construction processes can cause soil and ground contamination, atmospheric emissions, waste generation, resource consumption, and more (Gangolells, et al., 2009). One important environmental impact of the on-site construction phase is waste generation. In order to obtain a sensible reduction of onsite waste production, construction design and management should be well-planned, minimizing excess construction materials (Oka, et al., 1993). Asdrubali (Asdrubali et al., 2013) divided the construction phase into three sub-systems: the material production phase, building construction phase (the main topic of this section), and the “end-of-life” phase. In a Life Cycle Energy Assessment (LCEA) (Ramesh, et al., 2010) (Buyle, et al., 2013) (Cabeza, et al., 2014), the amount of energy used on-site for

Construction Industry Total [PJ]

Year

Gasoline [PJ]

Diesel [PJ]

Total [PJ]

Light Trucks (on-highway)

1997

6260

250

6510

400

2002

6940

270

7210

3440

Medium/Heavy Trucks (on-highway)

1997

490

3820

4310

740

2002

600

4690

5290

910

Construction Equipment (off-highway)

1997

38

700

740

740

2002

36

800

840

840

1997

6790

4770

11550

1880

2002

7570

5760

13330

2190

Total

Table 7.1: 1997 and 2002 Estimates of Gasoline and Diesel Use for Construction in Petajoules in the US, per Year Source: Sharrard, et al., 2007 78 | Transportation and On-site Energy Use

building construction is computed in the Initial Embodied Energy (IEE: energy “contained” in all the materials used in the building and technical installations) that contributes to the determination of the Life Cycle Energy (LCE) value, together with Recurring Embodied Energy (REE: energy involved with the repair and replacement/rehabilitation of the building), Operating Energy (OE: energy used to maintain comfort conditions), and Demolition Energy (DE: energy from demolition and transporting waste to landfills) (Dixit, et al., 2012) (Plank, 2005). In order to reduce not only the operational energy demand, but also to ensure that attention is paid to the impacts caused by building construction, the minimization of initial embodied energy must be taken into account, especially for the design of buildings involved in a nearly-zero-energy design strategy. Construction phases are often neglected by LCA analyses (Sharrard, et al., 2008) (Srinivasan, et al., 2014), but this value can be very important. Despite the fact that most of the energy consumed during the life of a building is concentrated on the “use phase” (with operational consumption caused by HVAC systems, lighting, etc.), an optimization of the construction site and the construction process can ensure that energy and material waste is minimized from the beginning of a building’s life cycle. It’s useful to note that in the United States, 30% of total energy consumption, 60% of electricity use, and 16% of potable water goes toward the operation of buildings (USGBC, 2009) (Haney, 2011). Total on-site energy consumption includes the sum of the energy needed for excavation (digging, excavation, and groundwork), the foundation construction process, material handling (with cranes), and pumping concrete to upper levels.


Constr. Phase

Energy Consumption

GWP [%]

Material Manufacturing

94.89 %

95.16 %

Transportation

1.08 %

1.76 %

On-Site Construction

4.03 %

3.08 %

Total

100%

100%

Most of the existing literature analyzes the “construction phase” in terms of environmental impacts, evaluating/ estimating the amount of polluting substances (NOx, CO, HC, SOx, etc.) emitted by “non-road” vehicles (Sharrard, et al., 2007), or trying to calculate this data with the EPA2004 formula (Ahn, et al., 2009) (Zhang, et al., 2014) (E.P.A., 2009) (see Table 7.1).

Table 7.2: Distribution of Energy Consumption and GWP in the Construction Phase of a Typical Residential Building Source: Hong, et al., 2014

Execution Phase

Percentage of CO2 Emission

Tower Crane

39%

Excavator/Backhoe

26%

Generator

15%

Steel Bending Machine

3%

Material Hoist

2%

Passenger Hoist

3%

Gondola

2%

Concrete Vibrator

1%

Submersible Pump

1%

F.S. Pump

2%

Vibrator Rammer/Plate Compactor

2%

Compaction Roller

3%

Rock Drill Machine

1%

Total

100%

Some literature focuses on the important role played by “site-operation” simulators to minimize waste, optimize working-time, and reduce economic costs (Olearczyk, et al., 2014) (Wong, et al., 2013) (Hasan, et al., 2013) (Hajibabai, et al., 2011).

Table 7.3: Distribution of Energy Consumption of On-Site Construction Equipment for a Case Study Residential Building from the Literature Source: Wong, et al., 2013 Execution Phase

Percentage

Pit Support Construction

59.40 %

Excavation

18.30 %

Site Cleaning

12.30 %

Backfill Rank

7.50 %

Dewatering Operations

2.50 %

Total Value

100.00 %

Table 7.4: Distribution of Environmental Impacts for an 11-Story Building in Beijing Source: Li, et al., 2010

Emission = Engine Power (hp) * Operating hours (hrs) * Emission Factor (g/hp-hr) * Load Factor

Some US construction industry energy consumption data collected in 1997 are available in the bibliography. From these, it is possible to note how, for that year, the construction industry represented 3.7% of industrial electricity purchases and 0.8% of overall electricity use in the U.S. In the same year, electricity purchased by the construction industry required 422,000 TJ of total energy (Matthews, et al., 2005). Another study (Sharrard, et al., 2007) compares 1997 and 2002 data on energy consumption related to the US construction industry, estimating the gasoline and diesel use for construction in PetaJoules (1015 J) (see Table 7.1). Some researchers have demonstrated the importance of considering the construction phase to obtain a more detailed evaluation of a LCA analysis. Hong et al. (Hong, et al., 2014), for example, demonstrated the following subdivisions of energy-consumption during the construction phase for a residential building (LCA modules A+B) (see Table 7.2).

Some research uses a holistic hybrid model to evaluate a LCA (O’Donnell, et al., 2013) (Sharrard, et al., 2008). There are also studies that try to explain the importance of optimizing tower crane operations (Huang, et al., 2011) (Hasan, et al., 2013), excavation strategies (Hudson, 1993), and workplace optimization (Ismail, et al., 2013), to ensure optimal work conditions (minimizing waste and pollutant emission). Research on low-carbon construction processes (Wong, et al., 2013), which are based on a case study of a residential building, demonstrated that the main cause of “CO2 emissions” in the construction phase are tower-cranes and excavation equipment (see Table 7.3). Another case study (Li, et al., 2010) based on an 11-story reinforced concrete frame building (45 meters, 48,036 m2) built in Beijing, demonstrated the following percentages regarding the total environmental impact of the construction phase (Table 7.4).

“Transportation and on-site operations are often omitted from many analyses... due to the assumption that such operations play a marginal role on the environmental impact of buildings.”


Transportation and On-site Energy Use | 79

In this particular case, the largest amount of energy consumption belonged to excavation and site-clearing operations, because those operations required the use of heavy equipment such as bulldozers, trucks, and steamrollers, which require a large amount of diesel fuel. It is important to note that excavation and site-clearing operations are related to the specific case of each building site, and determining average values of energy-consumption data is difficult. As shown (Haney, 2001), one of the most effective strategies to ensure lower energy consumption and emissions is characterized by the list reported in see Table 7.5. Another author (Ko, 2010) suggests a “to do list” to make the construction phase as sustainable as possible: •

Choose the right machine for the task – avoid inefficiently oversized machines

“For the purposes of this research, it was assumed that most sources of on-site energy consumption would be constant throughout all of the studied solutions.” 80 | Transportation and On-site Energy Use

• • • •

Select equipment that is more fuel efficient Service equipment correctly Use sustainable, low carbon fuels Operate equipment efficiently (e.g. minimize idling time and using an appropriate amount of power)

In 2002, the US construction industry was one of the highest emitting sectors, producing approximately 1.7% of total US GHG emissions (equivalent to 6% of all US industrial sectors). In the same report, the EPA subdivided GHG emissions into three sub-categories: fossil fuel combustion, purchased electricity, and non-combustion activities. Construction industry GHG emissions are subdivided in the following tables using these classifications (see Table 7.6 and Table 7.7). One of the main goals of construction phase optimization should be the reduction of waste and the minimization of impacts on the local community. A carefully designed process that makes these considerations can, at the same time, minimize waste directed to landfills and also save money by providing an efficient, safe, and expedient construction process (Plank, 2005). For the purposes of this research, it was assumed that most sources of on-site energy consumption would be constant throughout all of the studied solutions. In fact, energy consumption related to site clearing, the construction of foundations, worker-related services, and lighting is not connected with building materials. However, it must be acknowledged that some differences exist in the vertical movement of building materials for the structural system, and that a different amount of energy for the hoisting of materials and pumping of concrete has been considered for each scenario.

Procedures

Percentage of Reduction for Construction Phase Energy Consumption and CO2 Emissions

Sourcing Materials Within 500 Miles

17.5%

Shipping only Full Loads of Materials

8.5 %

Improving Site Logistics and Crane-Sizing to Reduce Erection Time

6.4 %

Switching from an 8-Hour to a 10-Hour Work Day

3.0 %

Total Reduction

35.4 %

Table 7.5: Possible Reductions in Total Construction Phase Energy Consumption and CO2 Emissions Source: Haney, 2011

As seen in the existing literature (Goldenberg & Shapira, 2007) (Shapira, et al., 2007), there are five fundamental pieces of equipment needed during the on-site construction process: tower cranes, material handlers, concrete pumps, hoists/ lifts, and forming systems (decks, etc.). Unfortunately, little information is available in the literature that can contribute reliable and complete information for the specific case of tall building construction. In order to ensure useful and objective data of those on-site operations, two leading companies in the field of crane construction, Terex-ComEdil Cranes, and in the field of concrete pumps, Putzmeister, have been contacted to provide case-specific information to be inputted in the software model for the creation of the LCA analysis. Also, the transportation of materials varies significantly depending on their point of origin.


Fuel

Emissions [kg CO2 / unit materials]

Estimate of Sector-Wide Emissions Reductions* Using 3% Less Fuel

Using 10% Less Fuel

Diesel

2.79 kg CO2/liter

2.02 x 1 million tons CO2


Gasoline

2.34 kg CO2/liter



Propane

1.52 kg CO2/liter

N.A.**

N.A.**

Natural Gas

0.19 Kg CO2/m3



Notes: Emissions factor for diesel and gasoline were converted from EPA’s 2008 Inventory of Greenhouse Gases 1999-2006, Table A-29 and A30. Emissions factor for propane and natural gas were converted from EIA data sources. MMTCO2 = million metric tons of CO2*. Estimate of possible emission savings from percentage reductions are based on 2002 fuel consumption estimates used in the EPA report, Quantifying Greenhouse Gas Emissions in Key Industrial Sectors in the U.S. (May 2008). Numbers presented are for the purpose of illustrating the magnitude of possible reductions only and should not be interpreted as absolute quantities. No economic census data are available to estimate sector-wide propane consumption. N.A.** = Data not available. All numerical value are converted to the international metric system, assuming: 1 US gallons liquid = 3.7845 liters; 1lb = 0.45359 Kg; 1 ft3 = 0.028317 m3)

Table 7.6: GHG Emissions Reduction Scenarios from Reduced Fossil Fuel Use for the US Source: E.P.A., 2009

Emissions Source

Million Metric Tons of CO2Eq.

Percent of Total

Fossil Fuel Combustion

100

76%

Purchased Electricity

31

24%

Total

131

100%

Table 7.7: US Construction Sector Greenhouse Gas Emissions, 2002 Source: E.P.A., 2009

For this reason, these two items of energy consumption have been assessed with greater detail in order to provide a casespecific result for each analyzed scenario.

A travel distance of 2 kilometers was assumed for concrete, which would be transported by a mixer truck (with a gross weight of 28 tons) from the nearest cement plant.

7.2 Transportation For energy consumption (and its relative environmental impacts), all considerations and values in this report are derived from the available data of the construction process for the identified case study (300 North LaSalle, as illustrated in Section 3.4).

Structural steel sections were assumed to travel 163 kilometers, equivalent to the distance between the hypothetical building site and the nearest steel producer. That distance is reduced to 98 kilometers for steel studs and metal decking, which can be moved either with a small truck with

a 7.5-ton capacity or bigger one, with a gross weight of 30–40 tons. Steel rebar and welded meshes were assumed to not only travel by truck (with a gross weight of 30–40 tons), but also by train (considering routes of 875 km for the steel rebars and nearly 1,700 km for the welded mesh). The energy consumption of debris transportation was also considered, with an assumed travel distance of 38 km in a truck with a gross weight of 12–14 tons for the concrete debris and 22 km (with the same kind of vehicle) for steel scraps (see Table 7.8). 7.3 Crane Operations Cranes perform one of the most important roles during the construction phase. Given the scarcity of scientific literature about this topic (the bulk is concentrated almost exclusively on the placement of cranes and their optimization in terms of management), in order to be able to objectively assess their energy consumption, some casespecific information was obtained from Terex-ComEdil. Some considerations have to be made in order to establish an accurate estimate of a crane’s environmental impact during the construction of a tall building. The crane’s operations during the construction phase of a building are not limited to the hoisting of materials, but they are used for a large extent of on-site material handling. Thus, the use of a simple parameter is not viable (i.e. Kw/ton/meter of height) to assess their global energy requirement. Tall buildings require custom-designed cranes for their construction that must be designed in parallel with the design of the structures themselves. This optimizes construction times, reduces construction costs, and minimizes energy consumption.



It’s important to observe that these cranes (which are designed specifically for each building) experience a significant amount of wear by the end of the construction phase. It is often impossible to reuse them for the construction of another building. The dismantling of the crane should be anticipated in the design phase in order to minimize the risk of damaging the building’s façades and those of surrounding buildings. One of the most important pieces of data needed to evaluate energy consumption of cranes is the duration of the construction period. In order to calculate these values, durations of 18 months for the 60-story tower (246 meters) and 36 months for the 120-story tower (490 meters) have been assumed based on a comparison with similar projects, with an assumed 12 hours of operation per day and 30 days per month. Such durations may seem shorter than the on-site construction of similar tall buildings, but this case only considers the construction time for structural systems, while in real building sites, construction proceeds on many simultaneous parts of a building. In order to estimate a precautionary value as close as possible to the real value, three scenarios were established with varying load cycles (maximum, medium, and minimum). An average is then calculated from these three values. Using product information available on company brochures, an energy consumption of 160, 100, and 40 kW/h can be assumed for crane operations on the 60-story structure during the maximum, medium, and minimum load cycles. Such schemes may be associated with the different materials used for the construction of the tower. Figure 7.1: One World Trade Center, 2014, New York City, during construction phase Source: Dario Trabucco

82 | Transportation and On-site Energy Use

Consequently, the maximum load scheme was used for the steel scenario, the minimum load scheme for the concrete


scenario, and the medium load scheme for the composite scenario. In this case, it must be remembered that the energy consumption of the concrete pumps will be added to the crane’s consumption in order to establish an estimate for the overall hoisting of materials. For 60-story scenarios: PowerMAX,MID,MIN* 18 months * 30 days * 12 hrs

A bigger crane needs to be used for the taller tower, as heavier structural elements will need to be hoisted to greater heights. In this case, the energy consumption of the crane is considered to be 190, 110, and 60 kW/h for the maximum, medium, and minimum loading schemes. However, such values are only provided for a 200-meter construction scheme, while the 120-story scenario is 490 meters in height. Thus, the final result needs to be multiplied by 2.4 (490/200) to account for the increased hoisting consumption.

Values Per Kg

Truck Distance [km]

Type of Truck

Train Distance [km]

Concrete

-

-

-

9-10ksi Concrete-C70

2

8ksi Concrete-C55

2

6ksi Concrete-C40

2

4-5ksi Concrete - C30/37

2

Structural Steel Components

-

Steel Beams

163

Mixer-Truck Up to 28 Ton Gross Weight

-

-

Truck-Trailer 30/40 Ton Gross Weight

2.4 * PowerMAX,MID,MIN* 36 months * 30 days * 12 hrs The results shown in the chart above have been used and inputted in the LCA models of each scenario as electricity coming from the grid. In some particular cases, however, an on-site diesel generator can provide the energy needed, but this case has not been assessed here. 7.4 Concrete Pumping As previously mentioned, a further important role is played by concretepumping systems during the on-site construction phase. Putzmeister, a global manufacturer of concrete pumps was contacted to obtain reliable average values of energy consumption.

-

-

For 120-story scenarios:

Steel Columns

163

Steel Trusses

163

Reinforcing Steel Components

-

-

-

Steel Rebar

228

875 1698

According to Putzmeister, different factors have to be considered: •

The concrete mix-design (water/ cement ratio, type of inert materials, quantity of fine particles in the mixture, and the presence or absence of certain additives) as well as external factors such as environmental temperatures play an important role regarding the friction factor of the concrete in the pipeline during the pumping phase.

•

Increasing distance or prevalence (height) increases the power required for pumping and, consequently, the fuel needed (in pumps driven by diesel engine) or electrical energy consumed (with electric motors).

-

WWF

2


Other Components

-

-

-

Steel Studs

98

Truck Up to 7.5 Ton Gross Weight

-

Metal Decking

98


-

Fireproofing Spray

N.A.

N.A.

N.A.

Demolition Waste

-

-

-

Concrete Debris

38

-

Steel Scrap

22

Truck 12/14 Ton Gross Weight

-

Table 7.8: Mode of Transport and Travel Distance for Materials Considered in the Study Source: CTBUH

Keeping this in mind, a common industry approximation assumes an



Figure 7.2: Deep-ground piles, like those at the Port of Tampa, Florida, US, can be extremely complex and expensive, which is why newer structures often re-use existing foundations Source: (cc-by-public domain) OTB

Hybrid Composite Structure

Story Count

RC Structure

60 st.

442 GJ

2,421 GJ

3,695 GJ

120 st.

6,515 GJ

11,887 GJ

21,604 GJ

have been developed in the past few years to facilitate their installation.

Steel Structure

However, formworks only have a marginal impact on the environmental balance of the construction process as their energy consumption is limited to transportation and hoisting. Their relatively low weight (compared to actual construction materials) makes them relatively lowimpact and the quantification of the formwork system is therefore excluded by this analysis.

Table 7.9: Crane Operation Energy Demand for All Case Studies Considered in this Research Source: CTBUH

energy consumption of 1 liter of diesel for each ton of concrete pumped at 100 meters. As pointed out several times by the manufacturer, this parameter lacks scientific relevance, as many factors influence the real equation. However, this rough estimate is used while speaking with clients in order to provide an estimate of the diesel that is used for concrete pumping.

In terms of their embodied energy, formworks must be considered instrumental goods (as cranes, trucks, concrete mixers, etc) and their deterioration and eventual replacement can be consequently excluded from the quantification of environmental impacts caused by the concrete construction system.

7.5 Formworks Formworks are needed in concrete buildings to create the shape of the cast for concrete elements before the concrete has cured to its final strength. These play a fundamental role in the construction of concrete buildings and the technology is rapidly evolving. The creation of a formwork system can often dictate the organization of a building site, and automatic systems 84 | Transportation and On-site Energy Use

7.6 Foundations As described in Section 1.3, different types of foundations exist in tall buildings as a consequence of the soil conditions under the construction site. The geologic conditions that characterize each site are so varied, even in the relatively small area of a city, that it is not possible to identify a representative foundation technology

that is widely applicable for the research. Similarly, the foundations of very tall building, or those that are located in areas where horizontal loads are important, may be required to oppose the drift caused by the building rather than preventing it from “sinking” into the ground. For this reason, it can be argued that heavier buildings require more foundation structures as, in some circumstances, the weight of the building prevents the overturning forces transferred to the ground. As a consequence, the different solutions available vary remarkably in terms of material use and necessary machinery, and an inventory of materials for the foundation structures would not be realistic. Also, it should be noted that foundations are rarely “demolished” at the end of a building’s life cycle. In fact, the removal of deep-ground piles and caissons would be extremely complex and expensive (see figure 7.2). On the contrary, existing foundations are often re-used for newer structures or, if they prove to be unsuitable for a new tall building, they can be “bypassed” with new piles dug in proximity to the old structure. Consequently, it would have been unpractical to account for the initial embodied energy of the building foundation, without the ability to include them in the end-of life scenario, as described in Section 8. Accordingly, all underground foundation structures are not included in the present research, and the above-grade structures are considered as sitting on their “ideal” conditions.





8.0 The End-of-Life of Tall Buildings


8.0 The End-of-Life of Tall Buildings

The CTBUH Skyscraper Center database (Council on Tall Buildings and Urban Habitat, 2015) shows that only seven buildings taller than 150 meters have ever been demolished to date (see Table 8.1). However, this list includes the two tallest buildings ever demolished, the World Trade Center Twin Towers, which collapsed as a consequence of the terrorist attacks of September 11, 2001, together with Seven World Trade Center that collapsed at the same time. Excluding these three cases, only four buildings taller than 150 meters have ever been voluntarily demolished, with the 187-meter Singer Building (demolished in 1969) holding the title of the tallest building ever dismantled, followed by the 1965 demolition of the Morrison Hotel in Chicago. Interestingly, the Deutsche Bank building in New York City and the One Meridian Plaza in Philadelphia (respectively the 6th and 7th tallest in the list) have been demolished, though not as proper demolition projects, but as a result of consequences suffered during two catastrophic events (9/11 for the former, and a fire occurring in 1991 for the latter).

Except for a few demolitions that cleared the way for the construction of bigger towers during the 1970s, one could say that significant tall buildings are almost never demolished. A number of options exist to rejuvenate old towers (Trabucco & Fava, 2013) and demolition is typically not the preferred response to the evolution of market needs, but more demolitions will likely take place in the future as many tall buildings are now approaching the end of their service lives. Fast growing economies are putting ever increasing pressures on city centers, with a continuous demand for new offices, luxury hotels, and trophy residences. While nobody argues that many iconic buildings are likely to grace a city’s skyline for centuries, evidence shows that typical tall buildings suffer from a much faster aging processes, not in terms of structural and material obsolescence, but in terms of functional obsolescence. One of the most striking examples may be the 142-meter Ritz-Carlton hotel in Hong Kong that was demolished a mere 16 years after construction to be replaced with a taller office tower as a consequence of Hong Kong’s booming office market.

8.1 High-Rise Demolition Techniques Implosions are the most dramatic way to demolish buildings and they have been adopted in a number of cases (Liss, 2000), especially in the US. At 125-meters, the Great Hudson Store in Detroit is the tallest building ever imploded. Though this system is still widely used, it is being banned in most downtown areas due to the heavy impact it has on the city in terms of dust and pollution. Even where it is allowed, assurance liabilities and preparative mitigation works on nearby buildings make this system unsuitable for large-scale tall buildings in dense urban environments. On February 2013, the 116-meter AfE Turm in Frankfurt, Germany was imploded, making this the secondtallest building ever demolished with explosives, though it likely had a bigger volume than the Great Hudson Store. A slight variation of the implosion system is the controlled collapse system, which has been applied at its largest scale on a 14-story residential block in Vitry-surSeine, France. With this method, the load bearing structural system of the building is weakened in a convenient location

Building Name

City

Height

Year of Demolition

Reason for Demolition

One World Trade Center

New York City (US)

417 m

2001

Uncontrolled collapse due to terroristic attack

Two World Trade Center

New York City (US)

415 m

2001


Singer Building

New York City (US)

187 m

1968

Demolished to make room for 1 Liberty Plaza

Seven World Trade Center

New York City (US)

174 m

2001


Morrison Hotel

Chicago (US)

160 m

1965

Demolished to make room for the First National Bank Building (now Chase Tower)

Deutsche Bank

New York City (US)

158 m

2011

Irreparable damages caused by previous terroristic attack

One Meridian Plaza

Philadelphia (US)

150 m

1999

Irreparable damages caused by fire

Table 8.1: Recent Cases of Demolished Tall Buildings (italics denote buildings demolished through catastophic events) Source: CTBUH 88 | The End-of-Life of Tall Buildings


through pull-cables or hydraulic rams until the tower collapses on itself. The weight of the falling structure above the collapse point crushes the lower portion with an effect similar to the use of explosives. Though this system is less dangerous in some ways, it creates the same problems as explosives and is therefore unsuitable in dense urban environments.

Figure 8.1: Kajima Demolition Method applied at the Kajima HQ, Japan Source: Kajima Corporation

Figure 8.2: Taisei Corporation’s Ecological Reproduction System (Tecorep) applied at the Grand Prince Hotel, Japan Source: Taisei Corporation

Building Name

Height

Duration of Demolition Works

Notes

Deutsche Bank, New York

158 m

48 months

Actual duration of 47 months, demolition halted for 9 months due to a fire

One Meridian Plaza, Philadelphia

150 m

24 months

-

Ritz-Carlton, Hong Kong

142 m

12 months

Small floor plate

Hennessy Centre, Hong Kong

140 m

18 months

-

Table 8.2: Duration of Demolition Projects Source: CTBUH

Deconstruction (or dismantling) is a lessinvasive demolition method that can be applied to any kind of structure and is the most widely adopted system for tall buildings. Deconstructing tall buildings is a long term task that sometimes requires more time than was needed for the construction of the tower (see Table 8.2). Before demolition starts, the building must be protected with scaffolds to prevent falling debris. The scaffolding system can be “traditionally” supported from the ground (and attached to the main structure) or suspended from the roof of the building and jacked down as deconstruction proceeds downward. The latter option was extensively covered by the media in two very recent cases: the demolition of the 74-meter UAP Tower in Lyon, France as well as the 140-meter Grand Prince Hotel Akasaka and the Otemachi Financial Center, both in Tokyo (Kayashima, et al., 2012). Deconstruction requires the use of small excavators and other machines hoisted to the roof of a building. Structural elements are demolished through shears, torches, saws, and crushers. The limiting factors of this method is the load bearing capacity of the floor system (that needs to be able to carry heavy equipment and building debris), and the actual floor plan that may prevent the presence of multiple machines. Debris must be lowered with a crane and cannot usually be dropped via gravity into empty elevator shafts as this will cause vibrations, danger for the


The End-of-Life of Tall Buildings | 89

operators on the lower levels, and will wear out the lower portion of the shafts, threatening the structural integrity of the building.

dismantling method described above has been disregarded because it is not applicable to buildings at the scale of those considered in this study.

An even more spectacular demolition process was used for the deconstruction of the Kajima Corporation Headquarter complex in Tokyo. The two office towers (the tallest standing 85 meters) were demolished from the bottom up, lowering the whole building with hydraulic jacks and deconstruction proceeded on the bottom levels (Mizutani & Yoshikai, 2011) (see Figure 8.1).

Therefore, the technology that has been assessed in this study is a conventional top-down deconstruction method, which is similar to the techniques used in the largest demolition works to date.

For the purposes of this research project, demolition methods using explosives or a progressive collapse have not been considered due to their impossible applications on large-scale buildings in dense urban areas. Also, the bottom-up

8.2 Impact of Structural Materials on the End-of-Life of Tall Buildings Primarily, the impacts that structural materials have on the demolition process are time-related. Building debris must be lowered using a crane that usually has a capacity of 10 to 20 tons. Therefore, fewer crane operations are required for lighter buildings.

Entire bays of the steel frame are secured with steel cables to the remaining structure; they are torch cut and dragged inward with a skid drive, then cut into smaller pieces and lowered to the ground with the crane. Materials are lowered either as bundles of steel pieces or inside of a skip bucket. Concrete elements are partially cut with a concrete saw or are weakened with a hydraulic concrete crusher, then pulled inward with a small loader. Large structural elements can either be lowered with a crane, or crushed into smaller pieces and dumped into a skip bucket. Chutes can be used only for small amounts of materials and their use is normally unbeneficial in terms of time savings. Horizontal partitions (floors) are usually hammered from the level above or crushed from below, and small pieces of debris are usually dumped into large buckets before being lowered.

Figure 8.3: The Despe TopDownWay system applied at the Bluevale and Whitevale buildings in Scotland Source: Despe 90 | The End-of-Life of Tall Buildings


Expected Duration of Demolition Works in Months (for all 60-Story Buildings Considered in this Study) Company

Concrete Core + Steel Columns

Concrete Core + Composite Columns

Concrete Structure

Steel Diagrid Structure

Brandenburg

50* (17)

58* (19)

51* (17)

40* (13)

Despe

36** (15)

33** (14)

32** (13)

37** (15)

Taisei

16***

17***

19***

15***

*Figures based on a 10 hour shift per day, with 8 hours of actual work. In brackets: the duration based on a 24-hour active site. Brandenburg says overnight demolition is unlikely to be allowed in dense downtown areas.

•

Liabilities: A steel beam would need to be tested before being reused in a new building to ensure that the performance of the steel profile has not been diminished during its previous use.

•

Demolition process: Steel scrap is a valuable material, with a market value of $300–$400 per ton. New steel profiles are sold for a price that ranges between $500 and $700 per ton. During demolition and transportation, the extra care (in terms of equipment and labor) that would be required to prevent any damage to the existing steel profile would bridge the cost gap between new and reused steel profiles.

•

Cost: The reuse of steel profiles would increase the transportation and stocking cost of profiles, thus negatively impacting the economic convenience of reusing structural elements.

**Figures based on 10 hours of operation per day. In brackets: the duration based on 24-hour active site. ***According to Taisei, its Tecorep demolition system allows a noise abetment of 23db, thus allowing overnight operations.

Table 8.3: Expected Duration of Demolition Projects Source: CTBUH

The type of structural system and structural material is, according to an industry survey, the driving factor in standard demolition works where multiple options are available (Abdullah & Anumba, 2002). As this study excluded the implosion/controlled collapse scenarios for the above mentioned reasons, the only remaining option is the top-down dismantling of the structure. Methods of intervention and types of machinery vary according to the structural material of a building, but more importantly, the structure of a building largely impacts the duration of the demolition process. Concrete buildings are more complex to dismantle than steel buildings. Composite construction tends to vary, depending on whether the structural elements are demolished with a diamond cable (that cuts through all materials) or through the use of two different demolition technologies: a crusher to break concrete (to expose the steel profile), and a shear or a torch to cut the steel elements. The expected demolition times are described below, as provided by the three demolition companies involved in the survey (see Table 8.3).

Obviously, concrete is abundantly present in concrete buildings, but it also represents a significant share of the demolition waste related to steel buildings, as it is used in vertical partitions but, more importantly, on floor slabs above metal decking. The demolition of concrete elements produces a significant quantity of dust. All demolition works use large quantities of water that is sprayed on concrete during demolition to reduce the amount of dust. Additionally, Taisei uses an enclosed demolition environment that prevents dust from escaping the building site. Brandenburg’s study mentioned an expected water consumption of 350 liters per hour of operation. The untreated water goes into the soil/sewage system, liberally flowing down through the building. During cold months, water is added with an environmentally friendly additive that prevents freezing. One of the advantages associated with steel construction is the possible reuse of steel members from a demolished building. Though this is a possibility, there are a number of reasons that this practice is not realistic for tall building construction, described below:

8.3 Energy Use in Demolition Most of the energy consumed during the deconstruction of tall buildings is from the diesel fuel required to operate demolition machinery (skid steers, bobcats, etc.). Electricity is used to operate cranes, but as materials are lowered down, gravity significantly reduces energy requirements. The demolition plan inquiry returned by Despe for this research provided a list of the equipment needed for each scenario. However, several experts speculate that fuel cost is not a major concern in the demolition sector compared to other economic aspects like disposal/recycling costs, transportation, and liabilities, which can, with marginal variations, jeopardize the financial balance of a demolition job (see Table 8.4).



Equipment

Steel Frame with Concrete Core


All Concrete Structure

Whole Steel Structure

Caterpillar 330 or Similar (number)

2

2

2

1

Case C75 or Similar (number)

5

6

6

4

Bobcat T300 or Similar (number)

3

3

3

2

Diesel Daily Consumption (liters)

528

576

648

344

Total Diesel Consumption (Liters based job on duration)

440,000

430,000

480,000

290,000

Diesel Consumption (L/m2)

3.1 L/m2

3,0 L/ m2

3.4 L/ m2

2,0 L/m2

Table 8.4: Expected Fuel Consumption During the Demolition Phase (for All 60-Story Buildings Considered in this Study) Source: Despe

Model

Power

Average Fuel Consumption Liters/Year (EPA)

Approximate Fuel Consumption per Job (Liters)

Description

Manufacturer

Hydraulic Excavat.

Daewoo

130Lc

81kW

13,722

21,727

Hydraulic Excavat.

Daewoo

SK225

110kW

13,722

21,727

Hydraulic Excavat.

Daewoo

S55V

38kW

4,883

7,731

Hydraulic Excavat.

Daewoo

S75LC

39kW

4,883

7,731

Loader

Daewoo

Mega 400

210kW

25,044

39,653

Skid steer

Caterpillar

226

45kW

6,669

10,559

Skid steer

Caterpillar

226B

45kW

6,669

10,559

Skid steer

Caterpillar

246

55kW

9,353

14,809

Light Tower

Ingersoll Rand

L6

10kW

4,408

6,980

Compressor

Ingersoll Rand

P185WJD

35kW

-

-

Dozer

Komatsu

D31P-18A

53kW

6,669

10,559

Wheel Loader

Kobelco

550

82kW

13,722

Total Fuel Consumption if all Equipment was Continually in use (liters)

Table 8.5: Estimated Fuel Consumption During Demolition Phase of Deutsche Bank in N.Y. Source: EPA, 2009 and CTBUH

92 | The End-of-Life of Tall Buildings

21,727 173,762

As only one of the three consulted demolition companies provided estimates for diesel consumption, a benchmark value was needed in order to validate the results on the basis of the following information. A detailed list of the diesel-powered equipment used to deconstruct the remaining 26 stories of the Deutsche Bank Building in New York was obtained (Bovis Lend Lease, 2014) and provides a rough estimation of the total energy consumed by this equipment. Engine power information was retrieved from manufacturer catalogs and associated to the average annual fuel consumption of similar-sized construction equipment calculated for the U.S. Environmental Protection Agency (EPA) (Eastern Research Group, Inc., 2010). The EPA’s report lists the average fuel consumption measured by excavators and other diesel-powered construction equipment used on-site per year. This data matches values that were found in other sources (Abolhasani, et al., 2008) (see Table 8.5). The demolition phase of the remaining 26 floors lasted approximately 19 months and the actual surface area that was dismantled is estimated at about 82,600 m2, resulting in a maximum diesel consumption of 2.1 liters/m2, equal to 78 MJ/m2, very similar to the value provided by Despe for the all-steel scenario. Another literature value of 0.0612 MJ/kg was found (Doka, 2003) that corresponds, for a building the size of the Deutsche Bank building, to approximately 37 MJ/m2. Consequently, a value of 70 MJ/m2 will be considered realistic for the on-site demolition of a steel building, 120 MJ/ m2 will be considered for a concrete building, 115 MJ/m2 will be considered for a composite building, and 110 MJ/ m2 will be considered for buildings with a concrete core and steel columns.


Steel Frame with Concrete Core


All Concrete Structure

Whole Steel Structure

Burners on Site

3

3

1

4

Job Duration [months]

17

19

17

13

Total Oxygen Consumption [m3]

4,798

5,363

1,599

4,892

Total Acetylene Consumption [m3]

1,028

1,149

343

1,048

Table 8.6: Expected Man Power and Consumption of Steelwork During the Demolition Phase (for All 60-Story Buildings Considered in this Study) Source: Brandenburg

According to the initial expectations, it should be noted that these values represent a very small fraction of a building’s initial embodied energy. Taisei’s study mentions that electricity can be produced using a regenerative brake system on the crane that converts the kinetic energy of descending debris into electricity. Some results of the adoption of this system can be found in the literature (Kayashima, et al., 2012), but it is not possible to determine the exact amount of energy produced and fed back into the grid using this technique. However, it can be speculated that in the near future all cranes will be equipped with energy recovery systems that will annul any other source of electricity consumption for crane operations (i.e. floodlighting, axial rotation, etc). For this reason, we have assumed the on-site energy consumption of a crane’s operations to be null for the purposes of this study. 8.4 Transportation Assumptions for Debris When working in dense urban environments, the logistics of a building

site is an important consideration. In demolition works, crane capacity is a key factor as the loads of debris, when lowered, need to be directly loaded onto trucks. This is often necessary to avoid the multiple handling of debris (unnecessary loading/unloading of materials that would negatively impact the economics of the project) and to cope with the constraints of very small sites, where there is little room to temporarily stock materials. The demolition of the Deutsche Bank building benefited from a unique “tolerance” by New York City as a consequence of the 9/11 terrorist attacks. Nonetheless, the site area was limited and materials were temporarily stocked in the lower levels of the building. In normal conditions, on-site operations are limited and the crushing of concrete is often not allowed. Brandenburg mentions an ideal capacity of 10 tons for trucks, which match the loading capacity of the on-site crane. Buckets of debris are directly loaded onto the truck and further processed off-site. Crushed concrete, being a low-value material, requires accurate logistics, as small variations can cause a massive

difference in terms of profitability and environmental impacts (Marinkovic’, et al., 2010). For this research, two different transportation scenarios were imagined for end-of-life concrete: a primary recycling site, located 12 km west of the demolition site, accepts crushed concrete at $2.5 per ton. A second site accepts incoming loads free of charge, but it is 65 km west of the demolition site. Basically, the decision is assumed on the basis of the contractor’s internal organization. If there are enough trucks, materials can be hauled to the furthest location, otherwise the dumping fees of the closer site are accepted and savings are realized on fuel and operator costs. With a price of $300 per ton, end-of-life steel is a much more valuable material, and transportation costs are not really relevant (Doka, 2003). A scrap yard was identified 11 km from the demolition site. The environmental impacts of transportation were included in the LCA models based on the number of loads needed to haul all of the demolition materials to their recycling sites. As expected, on-site energy consumption is relatively small compared to other factors, including the environmental emissions that occur during the demolition of a building, such as the transportation of debris and recycling of materials (Martínez, et al., 2013). Determining the environmental consequences of steel cutting is not a straightforward process. An oxygen/ acetylene torch used for cutting thick steel profiles consumes an average of 1,400 liters of oxygen and 300 liters of acetylene per hour. No data was available for the demolition of the Deutsche Bank building. Fortunately, the number of required burners on-site was provided by the demolition companies that supported the present study. Brandenburg estimated the



number of staff required. If an actual cutting time equal to 10% of the hours worked is considered, total fuel consumption can be estimated (see Table 8.6). 8.5 Sources of Data on Tall Building Demolition The present research deals with scenarios for 246- and 490-meter-tall buildings. No published data on the demolition of tall buildings was found to describe the process, equipment used, and energy consumption required for the demolition of buildings at such magnitudes.

Figure 8.4: Gash Area of the Deutsche Bank Building, 1974, New York City Source: William Moore

“The inclusion of an end of life scenario in new tall building development plans, especially in quickly evolving markets, can lead to significant economic and environmental savings in the long run.” 94 | The End-of-Life of Tall Buildings

The goal and scope of this research is the definition of a comprehensive LCA for tall building structures. Other studies, which have been extensively covered in Section 7.0 describe the energy requirements and environmental impacts connected with the construction of tall buildings. But in order to have a comprehensive analysis, system boundaries have to be extended to include the end-of-life scenario. Even if demolitions are a very rare occurrence for tall buildings, it cannot be denied that every building, sooner or later, will be demolished. The demolition of buildings is a delicate task that needs to be accurately planned using the most modern techniques (Cheng & Ma, 2013); ideally, a demolition plan should be considered in the design and construction of every building. As noted previously, functional obsolescence is a driving factor in the demolition of tall buildings. The inclusion of an end-of-life scenario in new tall building development plans, especially in quickly evolving markets, can lead to significant economic and environmental savings in the long run. The 490-meter scenario assessed in this research would become, if it were built, the fifth-tallest building in the world. Due to its height, this building would be considered “iconic,” and an end-of-

life scenario is unlikely to occur in a reasonable time frame. On the contrary, the shorter 246-meter scenario wouldn’t be out of the ordinary in many cities in North America, Asia, and the Middle East. Consequently, an end-of-life scenario for this building is more realistic, and should be thoroughly planned and carefully considered early in the development phase. Therefore, this study assesses the demolition of the 246-meter case study, although this scenario is 50% taller than the tallest building ever dismantled as well as 80% larger (in terms of floor area) than the Deutsche Bank Building in New York. As no precedent case studies exist for the demolition of buildings of this size, original information had to be retrieved from market leaders in this very unique sector, and benchmarked against data on the Deutsche Bank Building demolition (see Figure 8.4). Comprehensive information is available on the Lower Manhattan Development Corporation website regarding the dismantling of the Deutsche Bank Building in New York (Anon., 2014). A 12-page demolition plan inquiry was prepared and distributed to three international demolition contractors that had previous experience in tall building demolition: Depse (Italy), Brandenburg (US), and Taisei (Japan). The demolition plan included schematic drawings and material quantities acquired through the structural design inquiry previously described. The requested information included the duration of the demolition work, labor/equipment needed, mitigation procedures envisaged, expected final cost, and other important metrics. The results from the demolition companies, which were presented in this section, should not be seen as a competitive comparison to identify the most convenient offer, but rather as three possibilities to complete a job that has never been done before.





9.0 Inventory of Materials and Research Results


9.0 Inventory of Materials and Research Results

9.1 The Assessment of Two Environmental Impacts As noted in Section 3.3, the scope of this study consists of the identification of the most sustainable structural system for tall and supertall buildings through a life cycle assessment. For the purposes of comparing the two alternatives, two impact categories are considered: Climate Change and Resource Depletion. Global Warming Potential (GWP) was selected as an indicator for Climate Change, and Embodied Energy (EE) was selected as an indicator for Resource Depletion. The reason for choosing these two impact categories is dictated by the initial goal of this research, which is to help designers and structural engineers in the selection of the most “sustainable” structural system for tall buildings. Sometimes, the wide-ranging definitions for the term “sustainability” can cause confusion. Sustainability, as it is generally understood by scientists, is the

“On average, steel scenarios have better environmental performance (lower Global Warming potential values), while concrete scenarios have a lower embodied energy.” 98 | Inventory of Materials and Research Results

intersection between social, economic, and environmental growth. However, in daily life, the term sustainability is narrowed only to the concept of environmental sustainability, as it is the aspect that has been historically neglected. Thus, studies on environmental sustainability seek to identify the impact of human actions on the environment, in terms of natural resource depletion and changes to the environment. Due to climatic changes that have occurred in recent years as a result of greenhouse gas emissions, many efforts in the field are focused on reversing this trend. Thus, it was an obvious choice to select Global Warming Potential (GWP) as an indicator for this research, because it provides an accurate indication of the environmental consequences, at a global scale, of the structural choices made by designers. With this knowledge in hand, the project team can take an informed approach to the structural design of a building with respect to its greenhouse gas emissions. However, the research team agreed that this indicator alone would have oversimplified the intricate goal of identifying the most “sustainable” structural solution. As a consequence, Embodied Energy (EE) was selected as an indicator of Resource Depletion. Energy is the driving force of life on earth, and the cause of many political, military, and strategic decisions internationally. Acknowledging the importance of energy broadens the definition of “sustainability” to account for the social and economic implications of energy consumption beyond purely environmental considerations. However, energy is profoundly linked to environmental aspects too, as the use of fossil fuels and other non-renewable resources cause large emissions of CO2 and other greenhouse gasses.

9.2 Comments on the Selected Indicators The decision was made to research all types of energy resources (and not just non-renewable resources) due to the fact that energy is traded on a global market, and it was found that renewables play a relatively small role in the satisfaction of the world’s needs . As a consequence, the research team believes that it is counterproductive to use a renewable source (i.e., hydro-electric power) to perform a heat-intensive process (like smelting iron or powering a cement kiln) where natural gas or other fossil fuels might be more effective. The hydro-electric power saved in this case can be more efficiently used in other applications where electric power doesn’t need to be converted (or converted back) into heat, thus reducing the inefficiencies of the process. The two main competing structural material industries (cement/concrete producers and steel producers) tend to have a different view on “sustainability.” Because the carbon emissions generated by cement are a result of the chemical reactions inherent in its production, the global warming potential of concrete suffers from a limited margin of improvement (unless cement substitutes are used) and, consequently, the cement industry tends to use embodied energy to indicate the sustainability of its products. On the contrary, the steel industry acknowledges the global warming potential of its products because emissions for steel can be reduced when a low-carbon source of energy (such as nuclear power or hydroelectricity) is used to power electric arc furnaces, thus resulting in a more “sustainable” product. The research results show that, as expected, concrete scenarios perform better from an embodied energy


perspective, while steel scenarios generally result in lower carbon emissions. Even in “all steel” scenarios, though, there is a significant volume of concrete in foundations and within the slab system. Similarly, in the “all concrete” building solutions there is a significant amount of steel in the form of rebar. Thus, a holistic look at all consumptive materials in any building solution must be considered with an agreement on the end boundary conditions. 9.3 Research Results The key research results are summarized in Table 9.1 and Figures 9.1 – 9.4, which represent the Global Warming Potential and Embodied Energy results of all 16 scenarios being considered. Each scenario was modelled by two different engineering firms, which provided an inventory of materials. The 32 resulting inventories were multiplied for the two different sets of characterization factors, so as to reflect the variable environmental impacts of concrete (due to the variability of concrete design mixes). Figures 0.3–0.6 represent the entire life cycle (A1–C3) as described by EN 15978, which corresponds to the whole construction phase, from the extraction of raw materials to the installation on the building.

Short Description

Scenario Number

GWP [kg CO2 Eq./m2]

EE [GJ/m2]

Building Height [story]

Normal Steel + Concrete Core

1a

222

2.4

60

High Strength + Concrete Core

1b

219

2.4

60


1c

216

2.3

60


2a

241

2.2

60


2b

209

2.0

60

All Steel Diagrid Normal Steel

3a

243

3.0

60

All Steel Diagrid HS Steel

3b

226

2.7

60

Composite Diagrid

3c

228

2.6

60


4a

361

4.1

120


4b

357

4.0

120


4c

308

3.3

120


5a

300

2.8

120

All Concrete Carrow and Deep Beams

5b

277

2.6

120


6a

431

5.2

120


6b

423

5.1

120

Composite Diagrid

6c

292

3.3

120

Table 9.1: Results of Research (Summary) Source: CTBUH

idea, thus leading to the use of an unusual amount of structural steel. 9.4 Comparison with Literature Results

It should be noted that the results of the 6a and 6b scenarios, which were supposed to correspond to the “all-steel diagrid scenario,” present two very different results from one engineering firm to the other. Both firms agree that the building has an unusual shape for this structural system. Consequently, one firm decided to add a concrete core to help the external diagrid withstand the horizontal forces acting on the building. The other firm over-designed the steel diagrid to maintain the “all-steel”

A small number of LCA studies on tall buildings have been found in published literature, some authored by members of this research team. In order to perform a comparison with their findings, the results of the A1–A5 phase of this research have been divided by the gross floor area of the studied scenarios (141,600 square meters and 446,250 square meters for the short and tall scenarios respectively). A comparison table with the literature sources is offered here (see Table 2.2, page 29).

Only a few prior studies consider buildings of similar heights to this research project. In some circumstances, the results of these studies evidence GWP and EE values significantly lower than those found in the literature case studies, but the following explanation can be provided to justify the discrepancies. The 60-story case studies of the research by Foraboschi (Foraboschi et al. 2014) are quite similar to the results of this study, and the discrepancy can be justified by a different building shape (square floor plan, 1:7 aspect ratio) and the different source of the characterization factors (Hammond & Jones 2008).


Inventory of Materials and Research Results | 99

60-story Equivalent Scenario - GWP (A1-C3)

35.000

30.000

118% 25.000

105%

102%

GWP [t CO2 Eq.]

100% 20.000

15.000

10.000

5.000

1a Normal Steel + Concrete Core

1a

1b

1b

1c

1c

2a

2a

2b

2b

All All All All Normal High High Concrete Concrete Concrete Concrete Concrete Concrete Steel + Strength + Strength + Core+ Core+ Wide and Wide and Narrow Narrow Concrete Concrete Concrete Composite Composite Shallow Shallow and Deep and Deep Core Core Core Frame Frame Beams Beams Beams Beams

3a All Steel Diagrid Normal Steel

3a

3b

3b

3c

3c

All Steel All Steel All Steel Diagrid Composite Composite Diagrid HS Diagrid HS Normal Diagrid Diagrid Steel Steel Steel

French Ready Mix Association A1-C3 GWP [t CO2Eq.]

22,057

19,194

21,902

18,831

21,564

18,766

21,592

27,298

18,988

23,147

23,542

21,812

21,399

21,115

22,751

19,453

US EPDs A1-C3 GWP [t CO2Eq.]

24,657

20,800

24,501

20,437

24,323

20,441

27,294

32,116

23,816

28,528

24,679

22,949

22,536

22,252

24,160

21,295

Figure 9.1: Life Cycle Assessment (Phases A1-C3: Raw Materials Extraction to Waste Processing) of the 60-Story Scenarios, Global Warming Potential Source: CTBUH

60-story Equivalent Scenario - EE (A1-C3)

350,000

300,000

116% 108%

105%

100%

250,000

EE [GJ]

200,000

150,000

100,000

50,000


1a

1b

1b

1c

1c

2a

2a

2b

2b


3a

3a

3b

3b

3c

3c



French Ready Mix Association A1-C3 EE [GJ]

244,424

216,702

242,404

211,972

235,764

209,916

207,121

279,177

185,091

238,914

289,123

266,519

261,258

257,472

270,043

225,903

US EPDs A1-C3 EE [GJ]

263,987

231,539

261,966

226,809

256,308

225,305

251,875

321,772

221,318

276,970

300,208

277,604

272,343

268,557

283,307

240,998

Figure 9.2: Life Cycle Assessment (Phases A1-C3: Raw Materials Extraction to Waste Processing) of the 60-Story Scenarios, Embodied Energy Source: CTBUH

100 | Inventory of Materials and Research Results


120-story Equivalent Scenario - GWP (A1-C3)

160,000

140,000

120,000

GWP [t CO2 Eq.]

118% 108%

100,000

105%

100%

80,000

60,000

40,000

4a

4a


4b

4b

4c

4c

5a

5a

5b

5b


6a

6a

6b

6b

6c

6c



French Ready Mix Association A1-C3 GWP [t CO2Eq.]

108,010

109,405

108,010

105,912

90,417

97,642

87,190

101,714

79,525

95,435

130,250

125,222

126,519

125,222

86,208

90,375

US EPDs A1-C3 GWP [t CO2Eq.]

119,482

125,225

119,482

121,731

103,182

116,491

107,845

125,841

97,610

116,991

133,592

144,832

129,860

144,832

95,780

101,294

Figure 9.3: Life Cycle Assessment (Phases A1-C3: Raw Materials Extraction to Waste Processing) of the 120-Story Scenarios, Global Warming Potential For Scenarios 6a and 6b Please See Disclaimer in Section “Results” of the Executive Summary Source: CTBUH

120-story Equivalent Scenario - EE (A1-C3)

1,800,000

1,600,000

1,400,000

123%

EE [GJ]

1,200,000

106% 1,000,000

100%

800,000

600,000

4a

4a

4b

4b

4c

4c

5a

5a

5b

5b

6a

6a

6b

6b

6c

6c





French Ready Mix Association A1-C3 EE [GJ]

1,219,233

1,227,723

1,219,233

1,182,238

961,564

1,039,256

847,854

988,060

782,172

940,617

1,637,140

1,393,478

1,588,556

1,393,478

965,166

1,017,568

US EPDs A1-C3 EE [GJ]

1,296,106

1,321,045

1,296,106

1,275,560

1,046,546

1,147,458

1,001,407

1,160,026

910,662

1,087,520

1,669,722

1,505,531

1,621,137

1,505,531

1,032,224

1,089,156

Figure 9.4: Life Cycle Assessment (Phases A1-C3: Raw Materials Extraction to Waste Processing) of the 120-Story Scenarios, Embodied Energy For Scenarios 6a and 6b Please See Disclaimer in Section “Results” of the Executive Summary Source: CTBUH



The 52-story building considered by Treloar (Treloar et al. 2001) uses characterization factors derived from a fundamentally diverse methodology (input-output). Also, the structural elements of this building represent a remarkable ratio with the total embodied energy of the building, suggesting an underestimation of the other building components (curtain wall, interior finishes, MEP, etc.). The concrete frame of a shorter 40-story building considered by Trabucco (Trabucco 2012) has an EE value that is twice the figures resulting from this research, but the case study considered in that paper (Palazzo Lombardia in Milan) has a very peculiar shape. Additionally, a hybrid analysis (consisting of a different methodology) was used to extract the characterization factors of the building materials, thus the characterization factors for each material may vary significantly. The GWP of the 40-story steel diagrid considered by Oldfied (Oldfield 2012)

is one and a half times higher than the 60-story diagrid considered in this research, but the building has a very iconic shape (30 St. Mary Axe, London) that might justify the discrepancy. Moreover, the study from Oldfield also includes the foundation quantities. The paper from Trabucco (Trabucco 2011) on the same building has a remarkably different result from this research (with a much higher difference ratio from the results obtained by Oldfield), but an input-output method was used to obtain the characterization factors. The above mentioned discrepancies attest to the critical issues related to the LCA methodology and the variability of the results mentioned in the first and second point of the general conclusion. 9.5 General Research Conclusions A summary of the research results can be found in the following section, where the main information on each studied building scenario is presented. Some general outcomes are presented below, which highlight the overall findings of the research:

“…horizontal components of structural frames, rather than vertical ones, are responsible for the greatest share of environmental emissions.” 102 | Inventory of Materials and Research Results

1 – After reviewing the results of the LCA analysis within the system boundaries of EN 15978 (thus without considering the credit for scrap), the conclusions cannot be generalized for the 60- and 120-story buildings and a clear “winner” cannot be identified in terms of an ideal structural material. On average, steel scenarios have better environmental performance (lower Global Warming potential values), while concrete scenarios have a lower embodied energy. This is especially true in the scenario variations that use the concrete environmental values for US cement production, which are higher than those of French production.

As explained in Section 5.1, cement not only produces CO2 as a consequence of the energy consumed during the production process, but also from the chemical reactions that transform limestone into clinker. Consequently, even if the production of cement is not very energy-intensive, its associated CO2 emissions are relevant. On the contrary, all of the CO2 emitted during the production of steel is a consequence of the energy needed for the production process. Thus, even in the hypothetical case that both materials are produced from a carbonfree source (i.e., nuclear or hydro-power), cement will always have a minimum value of CO2 emissions determined by the formula CaCO3 + Heat = CaO + CO2. It is important to note that for the 60-story scenario, all-concrete solutions perform worse (on average) than the other scenarios in terms of GWP, while all-steel scenarios are those with the highest EE. For the 120-story scenario, the discrepancies between the solutions are smaller, with the composite diagrid representing the best solution from a GWP standpoint, while all-concrete scenarios have the lowest average EE. 2 – Steel is a recyclable material. At the end of its life cycle, steel can be melted to produce new steel products, whose mechanical properties are identical to those of the previous product. On the contrary, the post-consumer life of concrete involves significant “downcycling.” Recycled concrete cannot be used for structural purposes and the most common use of recycled concrete is as ballast material for road and railway construction, with a significant loss of value from its previous life (see Table 9.2). Consequently, each tall building scenario can benefit from the recyclability of the


Characterization Factor Source

French Concrete Values

Environmentally Optimized Scenario

LCA Phase

Entire Life Cycle (Modules A1-C3)

Entire Life Cycle (Modules A1-C3)

Scenario Number (SF = Structural Firm)

GWP [t CO2 Eq.]

EE [GJ]

GWP [t CO2 Eq.]

EE [GJ]


1a_SF 01

22,057

244,424

-30%

-20%

1a_SF 02

19,194

216,702

-32%

-20%


1b_SF 01

21,902

242,404

-30%

-20%

1b_SF 02

18,831

211,972

-30%

-20%


1c_SF 01

21.564

235,764

-28%

-19%

1c_SF 02

18,766

209,916

-30%

-19%


2a_SF 01

21,592

207,121

-13%

-13%

2a_SF 02

27,298

279,177

-23%

-21%


2b_SF 01

18,988

185,091

-15%

-15%

2b_SF 01

23,147

238,914

-23%

-21%


3a_SF 01

23,542

289,123

-44%

-25%

3a_SF 02

21,812

266,519

-43%

-25%


3b_SF 01

21,399

261,258

-43%

-24%

3b_SF 02

21,115

257,472

-43%

-24%

3c_SF 01

22,751

270,043

-38%

-23%

Short Description

Composite Diagrid

3c_SF 02

19,453

225,903

-34%

-21%


4a_SF 01

108,010

1,219,233

-35%

-22%

4a_SF 02

109,405

1,227,723

-34%

-23%


4b_SF 01

108,010

1,219,233

-35%

-22%

4b_SF 02

105,912

1,182,238

-33%

-22%


4c_SF 01

90,417

961,564

-27%

-19%


4c_SF 02

97,642

1,039,256

-27%

-19%

5a_SF 01

87,190

847,854

-16%

-16%

5a_SF 02

101,714

988,060

-17%

-16%

All Concrete, Narrow and Deep Beams

5b_SF 01

79,525

782,172

-18%

-17%

5b_SF 02

95,435

940,617

-18%

-18%


6a_SF 01

130,250

1,637,140

-50%

-28%

6a_SF 02

125,222

1,393,478

-32%

-22%


6b_SF 01

126,519

1,588,556

-49%

-28%

6b_SF 02

125,222

1,393,478

-32%

-22%

6c_SF 01

86,208

965,166

-33%

-22%

6c_SF 02

90,375

1,017,568

-34%

-22%

Composite Diagrid

Table 9.2: Results of the A1-C3 phases (raw materials extraction to waste processing) of the research and comparison with the gains of the “environmentally optimized scenario” solution. Source: CTBUH

steel at the end of the building life cycle along varying magnitudes: concrete scenarios benefit from the recyclability of rebar (see Section 4.5), while steel buildings benefit from the recycling potential of a greater amount of steel, since the material represents a larger percentage of the total weight than in concrete scenarios. It means that a “credit” can be obtained for the steel parts forming the structure of a building. These include steel sections, rebar, steel decks, and so on. Some of the scenarios considered by this research produce such a high quantity of steel scrap that this “credit” is capable of offsetting the environmental “burden” caused by directing the remaining demolition waste (mainly concrete) to a landfill. However, European Norm 15978, which has been used as a reference in this study, prescribes that the system boundaries of a building LCA must be limited to the disposal of the demolition debris. However, it cannot be denied that most materials have a residual value even after the demolition of the building. In fact, it is not possible to “subtract” the credit from scrap from the environmental values of the other building phases (see Section 4.10). This is a highly disputed point of debate in the LCA community; several researchers are convinced that the credit from scrap should be included in the system boundaries of an LCA, as the recycling potential of materials should be considered in an environmental analysis to promote the use of recyclable materials. The steel industry is not the only industrial party pushing in this direction, as paper and plastic industries would also benefit from this option. On the other hand, those who believe that this information would be misleading if accounted for in an LCA also have solid arguments. Non-recyclable materials such as concrete and wood



60-story Equivalent Scenario - GWP (A1-D - Beyond the System Boundary in EN) 15978)

35.000

30.000

134%

GWP [t CO2 Eq.]

25.000

20.000

100%

101%

100%

15.000

10.000

5.000


1a

1b

1b

1c

1c

2a

2a

2b

2b


3a All Steel Diagrid Normal Steel

3a

3b

3b

3c

3c


French Ready Mix Association A1-D GWP [t CO2Eq.]

19,021

16,237

18,894

15,939

18,772

15,984

21,868

26,015

18,996

22,031

19,025

17,619

17,272

17,052

18,901

16,230

US EPDs A1-D GWP [t CO2Eq.]

21,621

17,843

21,493

17,545

21,531

17,659

27,570

30,833

23,824

27,413

20,162

18,756

18,409

18,188

20,310

18,072

Figure 9.5: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the 60-Story Scenarios, Global Warming Potential Source: CTBUH

60-story Equivalent Scenario - EE (A1-D - Beyond the System Boundary in EN 15978)

350,000

300,000

118%

111%

250,000

101%

106%

EE [GJ]

200,000

150,000

100,000

50,000


1a

1b

1b

1c

1c

2a

2a

2b

2b


3a

3a

3b

3b

3c

3c



French Ready Mix Association A1-D EE [GJ]

222,333

194,410

220,560

190,259

216,166

189,407

219,514

277,858

193,378

237,396

251,446

231,712

227,043

223,821

239,358

200,848

US EPDs A1-D EE [GJ]

241,895

209,247

240,122

205,096

236,710

204,796

264,269

320,453

229,606

275,452

262,531

242,797

238,128

234,906

252,621

215,943

Figure 9.6: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling ( (Additional Information Beyond the System Boundaries, According to EN 15978) for the 60-Story Scenarios, Embodied Energy Source: CTBUH



120-story Equivalent Scenario - GWP (A1-D - Beyond the System Boundary in EN 15978)

140,000

120,000

120%

100,000

123%

GWP [t CO2 Eq.]

100% 80,000

60,000

40,000

20,000


4a

4b

4b

4c

4c

5a

5a

5b

5b


6a

6a

6b

6b

6c

6c



French Ready Mix Association A1-D GWP [t CO2Eq.]

94,033

95,260

94,033

92,394

81,009

87,504

86,286

100,346

77,836

92,871

105,907

110,906

102,845

110,906

74,126

78,319

US EPDs A1-D GWP [t CO2Eq.]

105,505

111,079

105,505

108,213

93,774

106,353

106,942

124,472

95,921

114,426

109,248

130,516

106,187

130,516

83,698

89,238

Figure 9.7: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the 120-Story Scenarios, Global Warming Potential (For Scenarios 6a and 6b, See Disclaimer in Section 9.3) Source: CTBUH

120-story Equivalent Scenario - EE (A1-D Beyond the System Boundary in EN 15978)

1,600,000

1,400,000

1,200,000

117% 105%

100%

EE [GJ]

1,000,000

800,000

600,000

400,000

4a

4a

4b

4b

4c

4c

5a

5a

5b

5b

6a

6a

6b

6b

6c

6c





French Ready Mix Association A1-D EE [GJ]

1,115,316

1,123,142

1,115,316

1,083,224

900,964

973,652

875,454

1,016,402

797,704

953,253

1,428,242

1,291,760

1,385,602

1,291,760

874,949

927,962

US EPDs A1-D EE [GJ]

1,192,189

1,216,464

1,192,189

1,176,546

985,945

1,081,854

1,029,007

1,188,368

926,194

1,100,156

1,460,823

1,403,813

1,418,184

1,403,813

942,007

999,550

Figure 9.8: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the 120-Story Scenarios, Embodied Energy (For Scenarios 6a and 6b, See Disclaimer in Section 9.3) Source: CTBUH



do not receive any “benefit” in this case, but are given equal consideration as the recyclable ones, as no one benefits from its recycling potentialities . As a consequence, according to EN 15978, Module D (the part of an LCA that deals with the recyclability of materials) is considered important additional information for the environmental accounting of various options (ATHENA 2002). In this research, both approaches have been used: results are presented both by including and excluding the recycling potential of steel. If the credit for scrap is considered, the results change significantly. For the 60-story scenario, concrete solutions are those with the highest GWP and EE of all combinations, with mixed solutions (i.e., concrete core and steel or composite frame) resulting in the lowest environmental impacts. Composite diagrid, on the other hand, represents the best solution for the 120-story building scenarios (see Figure 9.5-9.8). The high recycling potential is an intrinsic value of steel and metals in general, and this “credit” should be communicated as part of the additional information necessary to make an informed decision on the environmental properties of the various design solutions assessed by this research (ATHENA 2002) (WorldSteel Association 2011) (American Iron and Steel Institute 2013). The impact of Module D is evident when the credit for scrap is included as in Figures 0.8-0.11. Module D, developed and presented within this study, is a suggested approach with clearly identified impacts for further consideration and evaluation. Establishing methods to apply the credit value for steel scrap is a recommended topic of further research. 3 – The transportation of both construction materials and demolition 106 | Inventory of Materials and Research Results

waste is not a very significant factor in a tall building LCA, with values typically ranging between 1–2.5% in terms of total GWP and 0.9–3.2% of total EE when only the construction phase is considered. This study accounted for the actual transportation distances of the materials that were used in the construction of the referenced case study. These impacts represent average values for a construction project of this magnitude. Following an in-depth analysis, it was found that most of the environmental impacts associated with transportation occur during the final delivery of the materials to the construction site, and not during the previous phases of their fabrication process. In fact, the delivery of structural materials to the construction site is typically carried out by dieselpowered trucks. While the other stages of their fabrication utilize more efficient transportation means (ships, barges, trains, etc.), especially when materials need to travel long distances. This reality makes it possible to obtain structural materials with better environmental performance, even if the producers are located far away. Construction materials can be transported across greater distances without a significant impact on the overall sustainability of the building structure, especially when long-haul transportation methods employ ships, trains, and other “energy-efficient” means of transport. 4 – Tall buildings are commonly held responsible for a substantial depletion of construction materials as a consequence of the “premium for height” described by F. Khan, which is the extra structural materials that are needed to support tall structures given the increased lateral forces acting on them due to earthquakes and wind. This is not arguable, but it should be noted in the case studies examined that horizontal structures

(beams, floor slabs, etc.) represent 50–80% of the building’s weight on the shorter 60-story scenarios, and 30–60% of the building’s weight in the taller 120-story scenarios. This indicates that horizontal components of structural frames, rather than vertical ones, are responsible for the greatest share of environmental emissions. This is independent of building height (see Tables 9.3-9.4). In fact, the horizontal structures forming the flooring system are repeated multiple times in a tall building (60 and 120 times in the considered scenarios) and their design is only marginally affected by the height of the building, as just a few of the horizontal beams come into play with the vertical structure. Consequently, the materials being used for floors are not a consequence of the building’s height but, rather, of its structural spans . Also, it is very important to note how an optimization of the horizontal structures, which are repeated many times on each floor, can significantly reduce the amount of required structural materials, and their consequent environmental emissions. These reductions can be realized if shorter structural spans are used (the studied scenarios had 13.5 meters of unobstructed lease span) or lighter flooring systems are adopted. 5 – Significant environmental benefits can be realized by choosing the best material production process, as the same material can have profoundly different environmental properties depending on its source. A special set of characterization factors was used to run “environmentallyoptimized” scenarios. In this additional set of environmental data, the best environmental properties for metallic materials were used. Most of the steel products (steel profiles ASTM A913, rebar, etc.), for instance, can be purchased from


electric arc furnaces, which use recycled steel scrap as their predominant material input. The environmental properties of such products are extremely beneficial, and the resulting building structures designed with these materials have a GWP and EE significantly lower than the original structures designed with the average environmental values provided by WorldSteel (WorldSteel Association 2011) (Hammond & Jones 2011). Additionally, special design mixes of concrete can be used to improve the environmental properties of structures. In fact, a significant percentage of cement in the mix can be substituted with components such as fly ash, furnace slag, or silica fume, significantly decreasing the GWP and EE of the resulting concrete. Also, the production process can use unconventional materials to substitute the conventional fossil fuels needed to produce heat in the kiln. In fact, post-consumer plastics such as used tires and other by-products can be used as a combustion material. The environmental benefits of this procedure, however, are difficult to account for in terms of their relative emissions. Scientists have not yet agreed whether the relative environmental impacts caused by the combustion of such alternative fuels should be credited to the original product, for instance a tire, or if it should be accounted for in the life cycle of the new product as a combustion material. If the former system is used, the resulting cement is virtually a zero-energy material and the only carbon releases are those associated with the chemical reaction that transforms limestone into cement. If the latter system is used, the same concrete is not an environment-friendly material due to the many pollutants that are released during the burning process of unrefined combustibles.

However, for the purposes of this research, concretes with cement substitutes have not been considered. In fact, these types of concretes have different behavioral properties than “normal” concretes, such as longer curing times, possibly increased fragility, etc. (Bentz et. al. 2013) (Fantilli & Chiaia 2012). As a result, these alternatives were not considered in this research in order to improve the comparability of the various scenarios. However, it should be noted that cement substitutes are being used in the construction of tall buildings when special characteristics are required (e.g., in hot climates, fly ash is used to reduce the heat of hydration when large quantities of concrete are poured) and they are consequently worthy of further consideration and research in terms of their environmental implications for tall building structural systems (see Figures 9.9-9.12).

of knowledge: from general/conceptual aspects related to the planning and design of tall buildings, to precise aspects related to the choice of construction materials and their use. •

A study to explore the real needs of tenants in terms of column-free structural spans in tall buildings. Tall buildings are often designed with the longest unobstructed spans possible to increase adaptability for final users. This brings about suboptimal design solutions that require extra structural materials on elements (floor beams) that are repeated thousands of times in a tall building. This particular typology is strongly driven by the market, and any research on the drawbacks of reducing the unobstructed lease span in tall buildings must carefully consider the market disadvantages (if any) of buildings with shorter spans.

•

Similarly, a study on the optimal inter-story height would lead to significant savings in terms of structural materials; though it would contain the same available floor surface, a shorter building with optimized floor heights is subject to less forces, thus allowing a reduced quantity of structural materials for its vertical structures. Additionally, a shorter building has shorter vertical structures, thus significantly reducing the quantity of materials for structures and other building components: smaller façades, shorter ducts, etc. In order to achieve this, several strategies have to be studied and assessed. Acknowledging that tall buildings are market-driven projects, research should be carried out on the requested ceiling height by tenants. Once this is minimized without compromising the real

9.6 Future Research As mentioned before, the research results underline fundamental issues in the LCA methodology. Such problems are well known among LCA practitioners around the world. The most urgent issue, to increase the significance of LCA studies and extend their application, is to find solutions to the above-mentioned problems and inconsistencies. The identification of future research in this field is thus left to LCA specialists. However, there are many other research topics that can be developed and supported by the tall building industry. A list of potential research topics stemming from the results of this LCA is presented below. The list is noncomprehensive, but it consists of the most evident aspects of the practice that need accurate and urgent research. Topics are presented in a sequence that reflects their relative position in the flow



60-story Equivalent Scenario Environmental Optimization GWP (A1-D Beyond the System Boundary in EN 15978)

35.000

30.000

25.000

GWP [t CO2 Eq.]

169% 20.000

15.000

117%

109%

100%

10.000

5.000

1a Normal Steel + Concrete Core Environmentally Optimized A1-D GWP [t CO2Eq.]

15,330

1a

1b

1b

1c

1c

2a

2a

2b

2b

All All All All Normal High High Concrete Concrete Concrete Concrete Concrete Concrete Steel + Strength + Strength + Core+ Core+ Wide and Wide and Narrow Narrow Concrete Concrete Concrete Composite Composite Shallow Shallow and Deep and Deep Core Core Core Frame Frame Beams Beams Beams Beams 12,814

15,261

12,652

15,552

12,926

20,654

23,398

17,800

19,811

3a All Steel Diagrid Normal Steel 12,782

3a

3b

3b

3c

3c

All Steel All Steel All Steel Diagrid Composite Composite Diagrid HS Diagrid HS Normal Diagrid Diagrid Steel Steel Steel 11,982

11,834

11,677

13,787

12,529

Figure 9.9: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the “Environmentally Optimized” 60-Story Scenarios, Global Warming Potential Source: CTBUH

60-story Equivalent Scenario Environmental Optimization EE (A1-D Beyond the System Boundary in EN 15978)

350,000

300,000

250,000

114% 108%

200,000

105%

EE [GJ]

100%

150,000

100,000

50,000

1a Normal Steel + Concrete Core Environmentally Optimized A1-D EE [GJ]

200,969

1a

1b

1b

1c

1c

2a

2a

2b

2b


199,560

172,039

197,499

172,373

206,675

250,189

180,721

213,919

3a

3a

3b

3b

3c

3c



215,552

199,463

196,153

193,187

210,175

179,755

Figure 9.10: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the “Environmentally Optimized” 60-Story Scenarios, Embodied Energy Source: CTBUH



120-story Equivalent Scenario Environmental Optimization GWP (A1-D Beyond the System Boundary in EN 15978)

100,000

90,000

139% 80,000

122% GWP [t CO2 Eq.]

70,000

100%

60,000

50,000

40,000

4a Normal Steel + Concrete Core Environmentally Optimized A1-D GWP [t CO2Eq.]

72,136

4a

4b

4b

4c

4c

5a

5a

5b

5b

6a


72,136

72,635

67,982

73,578

80,262

93,194

71,862


85,404

64,786

6a

6b

6b

6c

6c

All Steel All Steel All Steel Diagrid Composite Composite Diagrid HS Diagrid HS Normal Diagrid Diagrid Steel Steel Steel 87,609

63,126

87,609

58,099

60,468

Figure 9.11: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the “Environmentally Optimized” 120-Story Scenarios, Global Warming Potential For Scenarios 6a and 6b Please See Disclaimer in Section 9.3 Source: CTBUH

120-story Equivalent Scenario Environmental Optimization EE (A1-D Beyond the System Boundary in EN 15978)

1,400,000

1,200,000

1,000,000

117% 105%

100%

EE [GJ]

800,000

600,000

400,000

200,000

4a Normal Steel + Concrete Core Environmentally Optimized A1-C3 EE [GJ]

978,686

4a

4b

4b

4c

4c

5a

5a

5b

5b


978,686

955,108

818,800

882,113

811,734

940,761

734,516

874,282

6a

6a

6b

6b

6c

6c



1,181,396

1,142,486

1,147,501

1,142,486

775,483

819,037

Figure 9.12: Results of the A1-D Phases: Raw Materials Extraction to Reuse, Recovery, and Recycling (Additional Information Beyond the System Boundaries, According to EN 15978) for the “Environmentally Optimized” 120-Story Scenarios, Embodied Energy For Scenarios 6a and 6b Please See Disclaimer in Section 9.3 Source: CTBUH



100,0%

261.114

59,7%

155.994

38,5%

100.417

252.406

100,0% 100,0%

374.213 179.502

100,0% 100,0%

374.213 182.652

100,0% 100,0%

467.008 401.392

100,0% 100,0%

530.341 465.805

100,0% 100,0%

341.253

147.286

58,4% 71,8%

268.629 73.800

41,1% 71,8%

268.629 76.950

42,1% 61,9%

289.194 222.460

55,4% 54,5%

289.194 222.460

47,8% 69,0%

235.387

100.417

39,8% 26,8%

100.417 100.417

55,9% 26,8%

100.417 100.417

55,0% 38,2%

178.578 179.696

44,8% 45,6%

241.910 244.108

52,4% 29,6%

Str. Firm B 6b Str. Firm A Str. Firm B 6a Str. Firm A Str. Firm B 5b Str. Firm A Str. Firm B 5a Str. Firm A Str. Firm B


100,0%

320.189 311.307

100,0% 100,0% 100,0% 100,0%

304.952 314.256 304.952 tons

Total Structural Weight

214.323

66,9% 65,9%

205.299 198.944

65,2% 66,3%

208.248 198.243

65,0% %

tons

Total Vertical Structures

31,6% 32,5%

101.163 101.163

33,2% 32,2% 33,2% %

101.163 tons

Total Horizontal Structures

Str. Firm B 4a Str. Firm A

Table 9.3 Influence of Horizontal & Vertical Structures Source: CTBUH

101.163

Str. Firm A Str. Firm B 4b Str. Firm A

73.152

100,0% 100,0%

57.763 69.875 58.070

100,0%

70.006

100,0%

tons Total Structural Weight

100,0%

101.163

4c

101.163

Str. Firm A

100,0%

55.713 42.801

100,0% 100,0%

42.916 43.386

100,0% 100,0%

44.722 111.875

100,0% 100,0%

106.870 134.250

100,0% 100,0%

128.785 60.112

100,0%

35,8%

19.949 6.895

16,1% 16,3%

7.010 7.480

17,2% 19,7%

8.816 50.997

45,6% 43,0%

45.992 51.457

38,3% 35,7%

45.992 24.094

40,1% 50,8%

37.134 21.693

37,6% 48,4%

33.806

48,5% %

37,9%

33.937 tons

Total Vertical Structures

22.000

34.419

47,1% 59,6%

34.419 34.419

49,3% 59,3% 49,2%

34.419 34.419

%

Str. Firm A Str. Firm B Str. Firm A

tons

Total Horizontal Structures

Str. Firm B

Str. Firm A

1c 1b 1a

Influence of Horizontal & Vertical Structures

Str. Firm B 6c

53.558

100,0%

33,2%

17.793

63,8% 61,3%

34.165 34.165

79,8% 79,6%

34.165 34.165

78,7% 76,4%

34.165 61.138

54,6% 57,2%

61.138

Str. Firm A Str. Firm B Str. Firm A Str. Firm B

61,9%

Str. Firm A Str. Firm B Str. Firm B

Str. Firm A

3a 2b 2a

83.053

A comprehensive study on flooring systems is needed to identify solutions that use less structural materials and, consequently, release less environmental pollutants. Innovative decking systems, both for steel and concrete buildings already exist, and some of these modern systems have already been adopted in tall buildings. Research is needed to assess their benefits, from more than just an environmental standpoint.

64,5%

•

83.053

The present research suffers from a lack of knowledge on demolition procedures for tall buildings due to the limited number of such demolitions that have taken place in the past. Research on the demolition techniques for tall buildings is needed to reduce the impact of this phase across several dimensions, both for the benefit of the owner/ developer (reducing the duration of demolition, its cost, and the liabilities toward other properties) and the surrounding community (in terms of noise/dust/vibrations during demolition and traffic congestion due to the removal of debris). Similarly, research is needed to design buildings that are easier to dismantle, which will ease this phase of a building’s life cycle.

57,3%

•

34.419

Str. Firm B

Str. Firm A

3c

Steel has an enormous advantage over concrete for the creation of modular, prefabricated elements that represent entire pieces of a building. Research should investigate these possibilities for their specific applications on tall buildings. Even if the credit for scrap cannot be considered within the building life cycle according to EN 15978, an easier assembly and dismantling of a tall building will have significant advantages, not only from an environmental perspective, but also in terms of costs, impacts on the city, and quality of construction.

3b

•


34.165

Str. Firm B

estate performance of the building, the inter-story height can be further optimized by reducing the space needed for the HVAC system and the height of the structural components. Research in this field would lead to significant advantages in the sustainability of tall buildings.

•

A study on the measurable influences (in terms of mechanical properties, cost, environmental benefits, etc.) of cement substitutes in the concrete mixes required for the construction of tall buildings would be beneficial. The research should not only assess the mechanical properties of the new concrete designs, but also the other parameters that influence the construction process: curing time, hydration heat release, fragility, and the ease at which it could be pumped at height.

•

Fireproofing is an essential component of steel construction. Due to the numerous fireproofing strategies that exist, research should be carried out to improve the environmental properties of fireproofing materials, especially with regards to their embodied energy and the ability to detach them from the steel structures after a building is dismantled. Currently, safety mandates call for a very strong bond between fireproofing materials and steel elements, making it very difficult to salvage the steel for recycling. Also, efforts should be taken to educate fireproofing companies on sustainability. The fireproofing contacts established during this LCA research showed little knowledge of LCA, embodied energy, and other assessment protocols of sustainability.

100,0%

261.114

81,8%

32,0%

213.652

83.543

Str. Firm B

Despite the fact that the reuse of steel elements at the end of a building’s life is more of an academic idea rather than a true possibility, buildings can be designed to maximize the ability to sort, reuse, and recycle materials at the end of their life cycles. From this perspective, composite columns seem to be a nonoptimal solution due to the strong connections that exist between large steel profiles, steel rebar, and studs, which make it very difficult and labor-intensive to separate these materials at the end of their lives.

100,0%

252.406

100,0%

100,0%

179.502

100,0% 100,0% 100,0%

467.008

100,0%

401.392 530.341

100,0% 100,0%

341.253

465.805

100,0%

182.652

374.213

374.213

82,7% 46,5% 96,0% 88,3%

96,2%

95,6%

95,3%

45,7%

83,6%

83,6%

208.779

33,1% 22,3%

313.004

46,5%

83.543

22,3% 45,7% 37,1%

444.915 383.714

44,8%

509.178

51,0% 24,5%

301.453

447.977

43,2%

83.543

313.004

83.543 83.543 173.232 237.496 83.543

237.496

173.232

83.543

83.543

Str. Firm A 6b

Str. Firm B Str. Firm A Str. Firm B 6a Str. Firm A Str. Firm B 5b 5a

Str. Firm A Str. Firm B Str. Firm A

320.189

100,0% 100,0%

311.307 304.952

100,0% 100,0% 100,0% %

314.256 304.952 tons


88,4% 82,9% 58,5% 82,2% 81,3% %

Total Concrete

26,1%

283.029 258.225

26,8% 27,4%

178.417 258.225

26,6% 27,4%

247.857

%

tons

83.543 83.543 83.543

Concrete 30-37

83.543

Str. Firm B 4b Str. Firm A Str. Firm B 4a Str. Firm A

tons

Str. Firm A

100,0%

73.152 57.763

100,0% 100,0%

69.875 58.070 70.006

100,0% %


tons

100,0%

86,8%

63.517 131.611

227,8% 84,9%

59.301

84,7%

82,8%

59.301

%

Total Concrete

tons

48.068

28.424

38,9% 49,2%

28.424 28.424

40,7% 48,9% 40,6% %

28.424 28.424 tons

Concrete 30-37

83.543

4c

Str. Firm B

55.713

100,0%

42.801

100,0%

42.916

100,0%

44.722

43.386

100,0%

111.875

100,0%

100,0%

134.250

100,0%

60.112

100,0%

128.785

106.870

100,0%

100,0%

75,5%

42.040

66,4% 66,2%

28.424

28.424 28.424

65,5% 94,1%

105.307

94,2%

96,7%

126.509

97,2% 84,7%

50.943

125.193

103.329

63,6%

28.424

28.424

51,0% 66,4% 66,2% 65,5%

28.424 28.424 28.424

63,6%

28.424 58.939

52,7% 55,1% 60,2% 62,7%

58.939 80.803 80.803

47,3%

28.424

83.543

6c

53.558

100,0%

80,2%

42.937

53,1%

28.424

Str. Firm B 3c Str. Firm A 3b

Str. Firm B Str. Firm A Str. Firm B 3a Str. Firm A Str. Firm B 2b Str. Firm A Str. Firm B 2a Str. Firm A Str. Firm B 1c Str. Firm A Str. Firm B 1b Str. Firm A Str. Firm B 1a Str. Firm A Influence of the Slabs

•

Table 9.4 Slabs Incidence Source: CTBUH




10.0 Appendix


Scenario 1a

60-Story Building – Concrete Core with Normal Steel Frame Scenario

Scenario 1a Description • The structure is composed of a reinforced concrete core and standard structural steel profiles (i.e. wide flange I-shapes). • The steel used for all structural elements is normal 50 ksi (345 MPa) steel • Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams are for gravity framing only (not lateral). • Beams are made of standard structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal deck with shear studs. Metal deck, beams and columns will include spray applied fireproofing.

Geometric Properties

Configuration

Layout

Scenarios

1a

Lobby

1

Lobby Height [m]

6

Mec. Floors

2

Mec. Floors Height [m]

8

Office Floors

56

Floor-to-Floor Height [m]

4

Total Floor Number

59

Height [m]

246

Width [m]

60

Length [m]

40

Lower Core Width [m]

35

Lower Core Length [m]

13

Lower Core Floors [story]

40

Upper Core Width [m]

16.5

Upper Core Length [m]

13

Upper Core Floors [story]

19

Gross Total Floor Area [m2]

141,600

Lower Net Area [m2]

77,800

Upper Net Area [m ]

41,525

Total Net Area [m2]

119,325

Built Floor Area [m2]

126,750

Number of Lower Columns

16

Number of Upper Columns

20

2

Columns

Number of Diagrid Columns Total Length of Columns

Table 10.1.1a: Geometric properties for Scenarios 1a Source: CTBUH

114 | Appendix


4,240

Quantities of Materials Material

Concrete

Steel

Scenario 1a Structural Firm 01

Property

Structural Firm 01 [tons]


10 ksi Concrete

11,944

-

9 ksi Concrete

0

0

8 ksi Concrete

12,857

7,608

6 ksi Concrete

6,077

12,036

4-5 ksi Concrete

28,424

28,424

Steel Rebar

1,388

957

WWF

260

260

Steel Studs

25

25

Metal Decking

1,212

1,212

Steel Beams

4,011

3,949

Steel Columns

1,971

1,614

French EPDs

LCA Modules

US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

Cradle to Gate

21,027

221,299

23,627

240,861

Cradle to Site

21,633

232,223

24,233

251,785

Cradle to Grave

22,057

244,424

24,657

263,987

19,021

222,333

21,621

241,895

Cradle to Cradle

(including recycling potential)

Table 10.3.1a: Results for Scenario 1a Structural Firm 01 Source: CTBUH

Scenario 1a Structural Firm 02 French EPDs

US EPDs

Steel Trusses

186

333

LCA Modules

Other

Fireproofing Spray

825

825

Cradle to Gate

18,252

195,363

19,858

210,200

Total

Above Grade Structural Weight

70,006

58,070

Cradle to Site

18,835

205,637

20,440

220,474

Scrap Input

6,357

5,827

Cradle to Grave

19,194

216,702

20,800

231,539

Total Scrap not Landfilled

8,898

8,218

16,237

194,410

17,843

209,247

Scrap

Cradle to Cradle


Net Scrap

2,541

Table 10.2.1a: Inventory of Materials for Scenarios 1a Source: CTBUH

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

2,391



Appendix | 115

150.000


232.223 betie

221.229 betie

200.000

not relevant during the use phase

100.000

241.895 epds

263.987 epds 244.424 betie

US EPDs Values

250.000

starting point of future life of the materials

222.333 betie

300.000

251.785 epds

[GJ]

232.223 betie

240.861 epds

Embodied Energy

251.785 epds

Scenario 1a: 60-Story Building – Concrete Core with Normal Steel Frame Scenario Structural Firm 01 Graphical Representation of the Research Result

50.000

10

50

60

Years

70


10.000

21.621 epds

24.657 epds 22.057 betie

24.233 epds



19.021 betie

15.000

US EPDs Values

21.663 betie

20.000

21.027 betie

[tons CO2eq]

24.233 epds

30.000

Global Warming 25.000 Potential

21.633 betie

23.627 epds

100.000

20

85.184

50.000

5.000

10

10.000

9.599

5.000

20

50

60

Transportation and on-site Construction

Years

70 demolition scrap recycling

Production of materials Recycled Input

Life Phase

Construction

PREVIOUS LIFE OF MATERIALS

LIFE CYCLE SYSTEM BOUNDARY

Global Warming Potential [tCO2Eq.]

116 | Appendix

BENEFITS AND LOADS BEYOND THE BUILDING LIFE CYCLE

(ACCORDING TO EN 15978) scenario 1a

Benefits of Using Recycled Inputs Embodied Energy [GJ]

Demolition

US EPDs French EPDs

-85,184

US EPDs French EPDs

Production Process 326,045 306,482

(ACCORDING TO EN 15978)

Transportation and On-site Operations

Incidence on Use Phase

Demolition

Credits for Scrap

10,924

N.A.

12,202

22,091

606

N.A.

424

3,036

33,226 -9,599

30,626


Scenario 1a: 60-Story Building – Concrete Core with Normal Steel Frame Scenario Structural Firm 02 Graphical Representation of the Research Result

100.000


231.539 epds 209.247 epds

150.000


216.702 betie 194.410 betie

195.363 betie

200.000

US EPDs Values

220.474 epds

250.000

205.637 betie

300.000

205.637 betie

210.200 epds

[GJ]

220.474 epds

Embodied Energy


50.000

10

20

50

60

Years

70

20.800 epds 19.194 betie


20.440 epds

10.000


18.835 betie

15.000

US EPDs Values

18.835 betie

19.858 epds

20.000

18.252 betie

[tons CO2eq]

20.440 epds

30.000



16.237 betie

100.000

17.843 epds

78.082

50.000

5.000

10 8.799

5.000 10.000

20

50

60


Years



Life Phase

Construction




US EPDs French EPDs

scenario 1a structural firm 02

-72,404

US EPDs French EPDs




Demolition





Demolition

Credits for Scrap

10,275

N.A.

11,065

22,292

582

N.A.

360

2,958

28,657 -8,799

27,051


Appendix | 117

Scenario 1b

60-Story Building – Concrete Core with High-Strength Steel Frame Scenario

Scenario 1b Description • The structure is composed of a reinforced concrete core and standard structural steel profiles (i.e., wide flange I-shapes). • The steel used for the columns is 65 ksi (F450 MPa) high strength steel, while all other structural elements use normal 50 ksi (345 MPa) steel. • Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams are for gravity framing only (not lateral). • Beams are made of standard structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal deck with shear studs. Metal deck, beams and columns will include spray applied fireproofing.


Configuration

Layout

Scenarios

1b

Lobby

1

Lobby Height [m]

6

Mec. Floors

2

Mec Floors Height [m]

8

Office Floors

56


4

Total Floor Number

59

Height [m]

246

Width [m]

60

Length [m]

40


35


13

Lower Core Floors [m]

40


16.5


13

Upper Core Floors [m]

19

Gross Total Floor Area [m ]

141,600

Lower Net Area [m2]

77,800

2

Upper Net Area [m ]

41,525

Total Net Area [m2]

119,325


126,750


16


20

2

Columns

Number of Diagrid Columns Total Length of Columns

Table 10.1.1b: Geometric Properties for Scenario 1b Source: CTBUH

118 | Appendix


4,240

Scenario 1b Structural Firm 01

Quantities of Materials Property



10 ksi Concrete

11,944

0

9 ksi Concrete

0

0

8 ksi Concrete

12,857

7,608

6 ksi Concrete

6,077

12,036

4-5 ksi Concrete

28,424

28,424

Steel Rebar

1,388

957

WWF

260

260

Steel Studs

25

25

Metal Decking

1,212

1,212

Steel Beams

4,011

3,949

Steel Columns

1,840

1,307

Steel Trusses

186

333

Other

Fireproofing Spray

825

825

Total


69,875

57,763

Scrap Input

6,246

5,567


8,770

7,915

Net Scrap

2,522

2,348

Material

Concrete

Steel

French EPDs

LCA Modules

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

Cradle to Gate

20,873

219,294

23,473

238,856

Cradle to Site

21,478

230,205

24,078

249,767

Cradle to Grave

21,902

242,404

24,501

261,966

18,894

220,560

21,493

240,122

Cradle to Cradle


Table 10.3.1b: Results for Scenario 1b Structural Firm 01 Source: CTBUH

Scenario 1b Structural Firm 02 LCA Modules

French EPDs

US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

Cradle to Gate

17,892

190,669

19,498

205,506

Cradle to Site

18,472

200,914

20,078

215,751

Cradle to Grave

18,831

211,972

20,437

226,809

15,939

190,259

17,545

205,096

Cradle to Cradle

Scrap

US EPDs



Table 10.2.1b: Inventory of Materials for Scenario 1b Source: CTBUH


Appendix | 119

200.000 150.000


261.966 epds 240.122 epds

US EPDs Values


242.404 betie 220.560 betie

219.294 betie

250.000

249.767 epds

300.000

230.205 betie

[GJ]

230.205 betie

238.856 epds

Embodied Energy

249.767 epds

Scenario 1b: 60-Story Building – Concrete Core with High Strength Steel Frame Scenario Structural Firm 01 Graphical Representation of the Research Result


100.000 50.000

50

60

Years

70

24.501 epds

21.493 epds

21.902 betie


18.894 betie

24.078 epds


10.000

24.078 epds

15.000


21.478 betie

20.873 betie

20.000

US EPDs Values

21.478 betie

30.000

Global Warming 25.000 Potential [tons CO2eq]

20

83.693

100.000

10

23.473 epds

50.000

5.000

10

5.000

50

60


-9.431

10.000

20

Years



Life Phase

Construction




120 | Appendix


(ACCORDING TO EN 15978) scenario 1b


Demolition

US EPDs French EPDs

-83,693

US EPDs French EPDs





Demolition

Credits for Scrap

10,911

N.A.

12,199

21,844

605

N.A.

423

3,008

32,904 -13,562

30,304


Scenario 1b: 60-Story Building – Concrete Core with High Strength Steel Frame Scenario Structural Firm 02 Graphical Representation of the Research Result

100.000



226.809 epds 205.096 epds

150.000

US EPDs Values

211.972 betie 190.259 betie

190.669 betie

200.000

215.751 epds

250.000

215.751 epds

300.000

200.914 betie

205.506 epds

[GJ]

200.914 betie

Embodied Energy starting point of future life of the materials

50.000

10

20

50

60

Years

70

20.437 epds 18.831 betie


20.078 epds

10.000


18.472 betie

15.000

US EPDs Values

18.472 betie

19.498 epds

20.000

17.892 betie

[tons CO2eq]

20.078 epds

30.000



15.939 betie

100.000

17.545 epds

74.593

50.000

5.000

10 8.406

5.000 10.000

20

50

60


Years



Life Phase

Construction




US EPDs French EPDs

scenario 1b structural firm 02

-74,593

US EPDs French EPDs




Demolition





Demolition

Credits for Scrap

10,245

N.A.

11,058

21,713

580

N.A.

359

2,892

27,904 -8,406

26,298


Appendix | 121

Scenario 1c

60-Story Building – Concrete Core and Composite Frame Scenario

Scenario 1c Description • The structure is composed of a concrete core and by composite steel/concrete columns on the perimeter. • The columns use standard structural steel sections with 50 ksi (345 MPa) strength as their core, covered with high strength 8-10 ksi (60-70 MPa) reinforced concrete. • Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams are for gravity framing only (not lateral). • Beams are made of standard structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal deck with shear studs. Metal deck, beams and columns will include sprayapplied fireproofing.


Configuration

Layout

Scenarios

1c

Lobby

1

Lobby Height [m]

6

Mec. Floors

2


8

Office Floors

56


4

Total Floor Number

59

Height [m]

246

Width [m]

60

Length [m]

40


35


13


40


16.5


13


19


141,600

Lower Net Area [m2]

77,800

Upper Net Area [m ]

41,525

Total Net Area [m2]

119,325


126,750


16


20

2

Columns

Number of Diagrid Columns

0

Total Length of Columns

4,240

Table 10.1.1c: Geometric Properties for Scenario 1c Source: CTBUH

122 | Appendix



Concrete

Steel

Scenario 1c Structural Firm 01

Property



10 ksi Concrete

13,032

0

9 ksi Concrete

0

0

8 ksi Concrete

13,844

8,758

6 ksi Concrete

8,218

13,761

4-5 ksi Concrete

28,424

28,424

Steel Rebar

1,554

1,122

WWF

260

260

Steel Studs

25

25

Metal Decking

1,212

1,212

Steel Beams

4,011

3,949

Steel Columns

786

667

French EPDs

LCA Modules

US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

Cradle to Gate

20,499

210,807

23,258

231,352

Cradle to Site

21,104

221,851

23,863

242,395

Cradle to Grave

21,564

235,764

24,323

256,308

18,772

216,166

21,531

236,710

Cradle to Cradle


Table 10.3.1c: Results for Scenario 1c Structural Firm 01 Source: CTBUH

Scenario 1c Structural Firm 02 French EPDs

US EPDs

Steel Trusses

186

333

LCA Modules

Other

Fireproofing Spray

800

800

Cradle to Gate

17.794

186.903

19,469

202,292

Total


73,152

60,112

Cradle to Site

18.376

197.268

20.051

212.657

Scrap input

5,467

5,138

Cradle to Grave

18.766

209.916

20.441

225.305


7,882

7,438

15.984

189.407

17.659

204.796

Scrap

Cradle to Cradle


Net Scrap

Table 10.2.1c: Inventory of Materials for Scenarios 1c Source: CTBUH

2,415

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

2,299



Appendix | 123

210.807 betie

200.000 150.000


256.308 epds 236.710 epds

US EPDs Values


235.764 betie 216.166 betie

250.000

242.395 epds

300.000

221.851 betie

[GJ]

221.851 betie

231.352 epds

Embodied Energy

242.395 epds

Scenario 1c: 60-Story Building – Concrete Core and Composite Frame Scenario Structural Firm 01 Graphical Representation of the Research Result


100.000 50.000

10

50

60

Years

70

24.323 epds

21.531 epds

21.564 betie


10.000


18.772 betie


23.863 epds

15.000

US EPDs Values

21.104 betie

20.000

20.499 betie

[tons CO2eq]

23.863 epds

30.000


21.104 betie

23.258 epds

100.000

20

73.256

50.000

5.000

10

10.000

8.255

5.000

20

50

60

Years

70 demolition


scrap recycling


Life Phase

Construction




124 | Appendix


(ACCORDING TO EN 15978) scenario 1c


Demolition

US EPDs French EPDs

-73,256

US EPDs French EPDs





Demolition

Credits for Scrap

11,044

N.A.

13,913

19,598

605

N.A.

460

2,792

31,513 -8,255

28,754



197.268 betie

186.903 betie

100.000




209.916 betie 189.407 betie

US EPDs Values

200.000 150.000

212.657 epds

250.000

197.268 betie

202.292 epds

300.000

212.657 epds

[GJ]

225.305 epds 204.796 epds

Embodied Energy

50.000

10

50

60

Years

70

20.441 epds

17.659 epds

18.766 betie



15.984 betie

10.000


18.376 betie

17.794 betie

15.000

20.051 epds

19.469 epds

US EPDs Values

20.000

18.376 betie

30.000


20.051 epds

100.000

[tons CO2eq]

20

68.854

50.000

5.000

10 7.759

5.000 10.000

20

50

60


Years



Life Phase

Construction




US EPDs French EPDs

scenario 1c

-68,854

US EPDs French EPDs




Demolition





Demolition

Credits for Scrap

10,365

N.A.

12,648

20,509

582

N.A.

389

2,782

27,228 -7,759

25,553


Appendix | 125

Scenario 2a

60-Story Building – All Concrete with Wide and Shallow Beams Scenario

Scenario 2a Description • The structure is composed of a concrete core and by concrete columns on the perimeter. The floor system is composed by a concrete slab with wide and shallow concrete beams. • Multiple grades of concrete from 4 ksi (30 MPa) to 10 ksi (70 MPa) are used for different structural components. The lightweight 4-5 ksi is used for floors, while the higher grades (6 ksi and up) are used for the lateral elements. All reinforcements are also made of normal 50 ksi (340 MPa) steel. • 220 mm rebar slab with PT/rebar band beams 2000 mm wide and 450 mm deep at 9 m off-center are used to match column lines. • Beams and floors are made of 4-5 ksi (30-37 MPa) with normal 50 ksi steel. • Disposable wooden formwork is considered beneath all the floors and beams .


Configuration

Layout

Scenarios

2a

Lobby

1

Lobby Height [m]

6

Mec. Floors

2


8

Office Floors

56


4

Total Floor Number

59

Height [m]

246

Width [m]

60

Length [m]

40


35


13


40


16.5


13


19


141,600

Lower Net Area [m2]

77,800

Upper Net Area [m ]

41,525

Total Net Area [m2]

119,325


126,750


16


20

2

Columns


0


4,240

Table 10.1.2a: Geometric Properties for Scenarios 2a Source: CTBUH

126 | Appendix



Concrete

Steel

Other Total Scrap


Property



10 ksi Concrete

24,150

5,962

9 ksi Concrete

0

0

8 ksi Concrete

13,340

31,464

6 ksi Concrete

6,900

8,280

4-5 ksi Concrete

80,803

80,803

Steel Rebar

3,332

7,481

WWF

260

260

Steel Studs

0

0

Metal Decking

0

0

Steel Beams

0

0

French EPDs

LCA Modules

GWP [t CO2Eq.]

EE [GJ]

US EPDs EE [GJ]

GWP [t CO2Eq.]

Cradle to Gate

20,526

180,198

26,228

224,952

Cradle to Site

20,813

187,977

26,516

232,731

Cradle to Grave

21,592

207,121

27,294

251,875

21,868

219,514

27,570

264,269

Cradle to Cradle


Table 9.3.2a: Results for Scenario 2a Structural Firm 01 Source: CTBUH Scenario 2a Structural Firm 02 LCA Modules

French EPDs

US EPDs

Steel Columns

0

0

Steel Trusses

0

0

Fireproofing Spray

0

0

Cradle to Gate

26,065

250,159

30,884

292,754

Cradle to Site

26,498

259,736

31,317

302,332

27,298

279,177

32,116

321,772

26,015

277,858

30,833

320,453


128,785

134,250

Scrap Input

2,507

5,403

Cradle to Grave Cradle to Cradle


3,412

7,354

Net Scrap

905

1,950



GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]



Appendix | 127

200.000

100.000


187.977 betie

150.000


264.269 epds


219.514 betie

US EPDs Values

207.121 betie

232.731 epds

232.731 epds

250.000

187.977 betie

300.000

224.952 epds

[GJ]

180.198 betie

Embodied Energy

251.875 epds

Scenario 2a: 60-Story Building – All Concrete with Wide and Shallow Beams Scenario Structural Firm 01 Graphical Representation of the Research Result

50.000

33.596

50.000

10

20

50

60

Years

70

27.294 epds

27.570 epds


10.000

21.592 betie


21.868 betie

26.516 epds

US EPDs Values

20.813 betie

15.000

26.516 epds

20.000

20.813 betie

[tons CO2eq]

26.228 epds

30.000


20.526 betie

100.000


5.000

10

3.786

5.000

20

50

60


10.000

Years



Life Phase

Construction




128 | Appendix




Demolition

US EPDs French EPDs

-33,596

US EPDs French EPDs





Demolition

Credits for Scrap

7,779

N.A.

19,144

-12,394

287

N.A.

779

-276

30,014 -3,786

24,312


US EPDs Values

300.000

200.000 150.000


259.736 betie

250.159 betie

250.000

321.772 epds 320.453 epds


279.177 betie 277.858 betie

[GJ]

302.332 epds

Embodied Energy

259.736 betie

292.754 epds

302.332 epds



100.000 50.000

32.116 epds

US EPDs Values

Years

70

30.833 epds

60

27.298 betie

50

31.317 epds

31.317 epds

72.404 30.884 epds

100.000

20

26.498 betie

10

50.000


20.000

26.498 betie

26.065 betie

[tons CO2eq]


26.015 betie

30.000


15.000 not relevant during the use phase

10.000 5.000

10 8.159

5.000 10.000

20

50

60


Years



Life Phase

Construction


Demolition





structural firm 02

Benefits of Using Recycled Inputs Embodied Energy [GJ] Global Warming Potential [tCO2Eq.]

US EPDs French EPDs

-72,404

US EPDs French EPDs




Demolition

Credits for Scrap

9,577

N.A.

19,441

1,319

433

N.A.

799

1,283

39,043 -8,159

34,224


Appendix | 129

Scenario 2b

60-Story Building – All Concrete Narrow and Deep Beams Scenario

Scenario 2b Description • The structure is composed of a concrete core and by concrete columns on the perimeter. The floor system is composed by a concrete slab with narrow and deep concrete beams. • Multiple grades of concrete from 4 ksi (30 MPa) to 10 ksi (70 MPa) are used for different structural components. The lightweight 4-5 ksi is used for floors, while the higher grades (6 ksi and up) are used for the lateral elements. All reinforcements are also made of normal 50 ksi (340 MPa) steel. • Beams 150 mm rebar slab with PT/rebar beams 400 mm wide and 450 mm deep at 3 m off-center. (assume pinned moment connection at core and perimeter for gravity system beam framing). • Beams and floors are made of 4-5 ksi (30-37 MPa) with normal 50 ksi steel. • Disposable wooden formwork is considered beneath all the floors and beams.


Configuration

Layout

Scenarios

2b

Lobby

1

Lobby Height [m]

6

Mec. Floors

2


8

Office Floors

56


4

Total Floor Number

59

Height [m]

246

Width [m]

60

Length [m]

40


35


13


40


16.5


13


19


141,600

Lower Net Area [m2]

77,800

Upper Net Area [m ]

41,525

Total Net Area [m2]

119,325


126,750


16


20

2

Columns


0


4.240

Table 10.1.2b: Geometric Properties for Scenarios 2b Source: CTBUH

130 | Appendix



Concrete

Steel


Property



10 ksi Concrete

24,150

33,782

9 ksi Concrete

0

0

8 ksi Concrete

13,340

6,955

6 ksi Concrete

6,900

5,631

4-5 ksi Concrete

58,939

58,939

Steel Rebar

3,281

6,309

WWF

260

260

Steel Studs

0

0

Metal Decking

0

0

Steel Beams

0

0

Steel Columns

0

0

French EPDs

LCA Modules

US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

Cradle to Gate

18,058

161,218

22,886

197,445

Cradle to Site

18,330

168,116

23,158

204,344

Cradle to Grave

18,988

185,091

23,816

221,318

18,996

193,378

23,824

229,606

Cradle to Cradle



Scenario 2b Structural Firm 02 French EPDs

US EPDs

Steel Trusses

0

0

LCA Modules

Other

Fireproofing Spray

0

0

Cradle to Gate

22,089

213,372

27,470

251,428

Total


106,870

111,875

Cradle to Site

22,468

221,623

27,850

259,678

Scrap Input

2,471

4,585

Cradle to Grave

23,147

238,914

28,528

276,970


3,364

6,240

22,031

237,396

27,413

275,452

Scrap

Cradle to Cradle


Net Scrap

Table 10.2.2b: Inventory of Materials for Scenarios 2b Source: CTBUH

892

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

1,655



Appendix | 131

Scenario 2b: 60-Story Building – All Concrete Narrow and Deep Beams Scenario Structural Firm 01 Graphical Representation of the Research Result

204.344 epds

204.344 epds 168.116 betie

250.000

197.445 epds

300.000

161.218 betie

[GJ]

US EPDs Values

221.318 epds 229.606 epds

Embodied Energy starting point of future life of the materials

100.000


168.116 betie

150.000


185.091 betie 193.378 betie

200.000

50.000

10

33.122

50.000

20

50

60

Years

70

23.816 epds

23.824 epds 18.996 betie

US EPDs Values

18.988 betie

[tons CO2eq]

23.158 epds


23.158 epds

22.886 epds

100.000


10.000


18.330 betie

15.000

18.330 betie

18.058 betie

20.000


5.000

10

3.732

5.000

20

50

60


10.000

Years



Life Phase

Construction




132 | Appendix




Demolition

US EPDs French EPDs

-33,122

US EPDs French EPDs





Demolition

Credits for Scrap

6,899

N.A.

16,974

-8,288

272

N.A.

658

-8

26,618 -3,732

21,790


300.000

US EPDs Values

276.970 epds 275.452 epds

[GJ]

259.678 epds

251.428 epds

Embodied Energy

259.678 epds

Scenario 2b: 60-Story Building – All Concrete Narrow and Deep Beams Scenario Structural Firm 02 Graphical Representation of the Research Result

221.623 betie

150.000


221.623 betie

213.372 betie

200.000

238.914 betie 237.396 betie

250.000



100.000 50.000

10

50

60

Years

70

28.528 epds

27.413 epds

23.147 betie


22.031 betie


27.850 epds

US EPDs Values

22.468 betie

27.850 epds

15.000

22.468 betie

20.000

27.470 epds

30.000


22.089 betie

100.000

[tons CO2eq]

20

61.436

50.000


10.000 5.000

10 6.923

5.000 10.000

20

50

60


Years



Life Phase

Construction


Demolition





structural firm 02


US EPDs French EPDs

-61,436

US EPDs French EPDs




Demolition

Credits for Scrap

8,251

N.A.

17,292

1,518

379

N.A.

679

1,116

34,393 -6,923

29,012


Appendix | 133

Scenario 3a

60-Story Building – All Steel (Normal Steel) Diagrid Scenario

Scenario 3a Description • The structure is composed of a diagrid of standard structural steel profiles. Core columns carry vertical loads only. Beams are composed of standard structural steel profiles. • The steel used for all structural elements is normal 50 ksi (345 MPa) steel. • Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams are for gravity framing only (not lateral). • Beams are made of standard structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal deck with shear studs. Metal deck, beams and columns will include spray applied fireproofing.


Configuration

Layout

Scenarios

3a

Lobby

1

Lobby Height [m]

6

Mec. Floors

2


8

Office Floors

56


4

Total Floor Number

59

Height [m]

246

Width [m]

60

Length [m]

40


35


13


40


16.5


13


19


141,600

Lower Net Area [m2]

77,800

Upper Net Area [m ]

41,525

Total Net Area [m2]

119,325


126,750


8


0

2

Columns


32


11,808


134 | Appendix



Concrete

Steel

Other Total Scrap


Property



10 ksi Concrete

0

0

9 ksi Concrete

0

0

8 ksi Concrete

0

0

6 ksi Concrete

0

0

4-5 ksi Concrete

28,424

28,424

Steel Rebar

548

548

WWF

260

260

Steel Studs

25

25

Metal Decking

1,212

1,212

Steel Beams

4,862

4,156

French EPDs

LCA Modules Cradle to Gate

US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

22,439

266,769

23,576

277,854

Cradle to Site

23,288

280,526

24,424

291,611

Cradle to Grave

23,542

289,123

24,679

300,208

19,025

251,446

20,162

262,531

Cradle to Cradle



French EPDs

US EPDs

Steel Columns

5,850

2,050

Steel Trusses

1,800

4,970

Fireproofing Spray

871

871

Cradle to Gate

20,723

244,325

21,860

255,410

Cradle to Site

21,560

257,951

22,697

269,037

21,812

266,519

22,949

277,604

17,619

231,712

18,756

242,797


44,722

43,386

Scrap Input

11,125

10,016



14,379

13,056

Net Scrap

3,255

3,040



GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]



Appendix | 135

291.611 epds

300.208 epds 262.531 epds 289.123 betie 251.446 betie

200.000


280.526 betie

250.000

US EPDs Values

280.526 betie

300.000

277.854 epds

[GJ]

266.769 betie

Embodied Energy

291.611 epds

Scenario 3a: 60-Story Building – All Steel (Normal Steel) Diagrid Scenario Structural Firm 01 Graphical Representation of the Research Result

150.000



100.000 50.000

10

50.000

20

50

60

Years

70

24.679 epds

20.162 epds

23.542 betie


10.000


19.025 betie

24.424 epds

24.424 epds

15.000


23.288 betie

20.000

US EPDs Values

23.288 betie

[tons CO2eq]

22.439 betie

30.000


149.071 23.576 epds

100.000

5.000

10

10.000

16.798

5.000

20

50

60

Years

70 demolition


scrap recycling


Life Phase

Construction




136 | Appendix




Demolition

US EPDs French EPDs

-149,071

US EPDs French EPDs





Demolition

Credits for Scrap

13,757

N.A.

8,597

37,677

848

N.A.

255

4,517

40,375 -16,798

39,238


200.000 150.000

277.604 epds 242.797 epds

244.325 betie

257.951 betie

250.000


266.519 betie 231.712 betie

300.000

US EPDs Values

269.037 epds

[GJ]

257.951 betie

255.410 epds

Embodied Energy

269.037 epds




100.000 50.000

10

50

60

Years

70

22.949 epds

18.756 epds

21.812 betie


10.000


17.619 betie


22.697 epds

15.000

US EPDs Values

21.560 betie

20.000

20.723 betie

[tons CO2eq]

22.697 epds

30.000


21.560 betie

21.860 epds

100.000

20

134.220

50.000

5.000

10

10.000

15.125

5.000

20

50

60


Years



Life Phase

Construction




US EPDs French EPDs

scenario 3a

-134,220

US EPDs French EPDs




Demolition





Demolition

Credits for Scrap

13,627

N.A.

8,567

34,807

837

N.A.

252

4,193

36,984 -15,125

35,848


Appendix | 137

Scenario 3b

60-Story Building – All Steel (High-Strength Steel) Diagrid Scenario

Scenario 3b Description • The structure is composed of a diagrid of standard structural steel profiles. Core columns carry vertical loads only. Beams are composed of standard structural steel profiles. • The steel used for the columns is 65 ksi (450 MPa) high strength steel, while beams and diagrid braces use normal 50 ksi (345 MPa) steel. • Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams are for gravity framing only (not lateral). • Beams are made of standard structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal deck with shear studs. Metal deck, beams and columns will include sprayapplied fireproofing.


Configuration

Layout

Scenarios

3b

Lobby

1

Lobby Height [m]

6

Mec. Floors

2


8

Office Floors

56


4

Total Floor Number

59

Height [m]

246

Width [m]

60

Length [m]

40


35


13


40


16.5


13


19


141,600

Lower Net Area [m2]

77,800

Upper Net Area [m ]

41,525

Total Net Area [m2]

119,325


126,750


8

2

Columns


0


32


11,808


138 | Appendix



Concrete

Steel


Property



10 ksi Concrete

0

0

9 ksi Concrete

0

0

8 ksi Concrete

0

0

6 ksi Concrete

0

0

4-5 ksi Concrete

28,424

28,424

Steel Rebar

548

548

WWF

260

260

Steel Studs

25

25

Metal Decking

1,212

1,212

Steel Beams

4,756

4,051

Steel Columns

4,250

1,640

French EPDs

LCA Modules

US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

Cradle to Gate

20,314

239,120

21,451

250,205

Cradle to Site

21,148

252,701

22,285

263,786

Cradle to Grave

21,399

261,258

22,536

272,343

17,272

227,043

18,409

238,128

Cradle to Cradle




US EPDs

Steel Trusses

1,700

4,900

LCA Modules

Other

Fireproofing Spray

870

870

Cradle to Gate

20,031

235,348

21,168

246,433

Total


42,916

42,801

Cradle to Site

20,863

248,918

22,000

260,003

Scrap Input

9,595

9,524

Cradle to Grave

21,115

257,472

22,252

268,557


12,591

12,478

17,052

223,821

18,188

234,906

Scrap

Cradle to Cradle


Net Scrap


2,996

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

2,954



Appendix | 139

150.000


272.343 epds 238.128 epds

239.120 betie

200.000

US EPDs Values

252.701 betie

250.000

261.258 betie 227.043 betie

300.000

263.786 epds

[GJ]

252.701 betie

250.205 epds

Embodied Energy

263.786 epds

Scenario 3b: 60-Story Building – All Steel (High-Strength Steel) Diagrid Scenario Structural Firm 01 Graphical Representation of the Research Result



100.000 50.000

10

50

60

Years

70

22.536 epds

18.409 epds

21,399 betie


10.000


17.272 betie


22.285 epds

15.000

US EPDs Values

21.148 betie

20.000

20.314 betie

[tons CO2eq]

22.285 epds

21.451 epds

30.000


21.148 betie

100.000

20

128.577

50.000

5.000

10

10.000

14.489

5.000

20

50

60


Years



Life Phase

Construction




140 | Appendix




Demolition

US EPDs French EPDs

-128,577

US EPDs French EPDs





Demolition

Credits for Scrap

13,581

N.A.

8,557

34,216

833

N.A.

252

4,127

35,940 -14,489

34,803


150.000


268.557 epds 234.906 epds

235.348 betie

200.000

US EPDs Values

248.918 betie

250.000

257.472 betie 223.821 betie

300.000

260.003 epds

[GJ]

248.918 betie

246.433 epds

Embodied Energy

260.003 epds

Scenario 3b: 60-Story Building – All Steel (High-Strength Steel) Diagrid Scenario Structural Firm 02 Graphical Representation of the Research Result



100.000 50.000

10

50

60

Years

70

22.252 epds

18.188 epds

21.115 betie


10.000


17.052 betie


22.000 epds

15.000

US EPDs Values

20.863 betie

20.000

20.031 betie

[tons CO2eq]

22.000 epds

21.168 epds

30.000


20.863 betie

100.000

20

127.617

50.000

5.000

10

10.000

14.381

5.000

20

50

60


Years



Life Phase

Construction




US EPDs French EPDs

scenario 3b

-127,617

US EPDs French EPDs




Demolition





Demolition

Credits for Scrap

13,570

N.A.

8,555

33,651

832

N.A.

251

4,063

35,548 -14,381

34,412


Appendix | 141

Scenario 3c

60-Story Building – Composite Diagrid Scenario

Scenario 3c Description • The structure is composed of a diagrid of composite steel/concrete members. • The columns and braces (all composite) standard structural steel sections with 50 ksi (345 MPa) strength as their core, covered with high strength 8-10 ksi (6070 MPa) reinforced concrete. • Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams are for gravity framing only (not lateral). • Beams are composed of standard shape structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal deck with shear studs. Metal deck, beams and columns will include sprayapplied fireproofing.


Configuration

Layout

Scenarios

3c

Lobby

1

Lobby Height [m]

6

Mec. Floors

2


8

Office Floors

56


4

Total Floor Number

59

Height [m]

246

Width [m]

60

Length [m]

40


35


13


40


16.5


13


19


141,600

Lower Net Area [m2]

77,800

Upper Net Area [m ]

41,525

Total Net Area [m2]

119,325


126,750


8


0

2

Columns


0


11,808

Table 10.1.3c: Geometric Properties for Scenarios 3c Source: CTBUH

142 | Appendix



Concrete

Steel


Property



10 ksi Concrete

0

6,049

9 ksi Concrete

0

0

8 ksi Concrete

0

5,221

6 ksi Concrete

13,617

3,243

4-5 ksi Concrete

28,424

28,424

Steel Rebar

778

1,188

WWF

260

260

Steel Studs

25

25

Metal Decking

1,212

1,212

Steel Beams

4,848

4,236

Steel Columns

3,050

610

French EPDs

LCA Modules

US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

Cradle to Gate

21,560

244,061

22,970

257,324

Cradle to Site

22,403

258,185

23,812

271,449

Cradle to Grave

22,751

270,043

24,160

283,307

18,901

239,358

20,310

252,621

Cradle to Cradle




US EPDs

Steel Trusses

1,900

1,490

LCA Modules

Other

Fireproofing Spray

800

800

Cradle to Gate

18,276

200,020

20,118

215,116

Total


55,713

53,558

Cradle to Site

19,105

214,015

20,947

229,110

Scrap Input

8,982

6,351

Cradle to Grave

19,453

225,903

21,295

240,998


11,911

8,873

16,230

200,848

18,072

215,943

Scrap

Cradle to Cradle


Net Scrap


2,929

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

2,522



Appendix | 143

244.061 betie

200.000 150.000


258.185 betie

250.000

283.307 epds

252.621 epds

US EPDs Values


270.043 betie 239.358 betie

300.000

271.449 epds

[GJ]

258.185 betie

257.324 epds

Embodied Energy

271.449 epds

Scenario 3c: 60-Story Building – Composite Diagrid Scenario Structural Firm 01 Graphical Representation of the Research Result


100.000 50.000

10

50

60

Years

70

24.160 epds

20.310 epds

22.751 betie


10.000


18.901 betie

15.000


23.812 epds

20.000

US EPDs Values

22.403 betie

21.560 betie

[tons CO2eq]

23.812 epds

30.000


22.403 betie

22.970 epds

100.000

20

120.353

50.000

5.000

10

10.000

13.562

5.000

20

50

60

Years

70 demolition


scrap recycling


Life Phase

Construction




144 | Appendix




Demolition

US EPDs French EPDs

-120,353

US EPDs French EPDs





Demolition

Credits for Scrap

14,124

N.A.

11,859

30,686

842

N.A.

348

3,850

36,532 -13,562

35,123


150.000 100.000



240.998 epds

US EPDs Values


225.903 betie 200.848 betie

200.020 betie

200.000

229.110 epds

250.000

214.015 betie

300.000

214.015 betie

215.116 epds

[GJ]

229.110 epds

Embodied Energy

215.943 epds


50.000

10

50

60

Years

70

21.295 epds 19.453 betie

18.072 epds

20.947 epds

US EPDs Values

19.105 betie

20.118 epds

30.000


20.947 epds

100.000


10.000


19.105 betie

15.000


16.230 betie

20.000 18.276 betie

[tons CO2eq]

20

85.104

50.000

5.000

10 9.590

5.000 10.000

20

50

60


Years



Life Phase

Construction


Demolition





structural firm 02


US EPDs French EPDs

-85,104

US EPDs French EPDs




Demolition

Credits for Scrap

13,995

N.A.

11,888

25,055

829

N.A.

348

3,223

29,708 -9,590

27,866


Appendix | 145

Scenario 4a

120-Story Building – Concrete Core with Steel (Normal Steel) Frame Scenario

Scenario 4a Description • The structure is composed of a reinforced concrete core and standard structural steel profiles (i.e. wide flange I-shapes). • The steel used for all structural elements is normal 50 ksi (345 MPa) steel • Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams are for gravity framing only (not lateral). • Beams are made of standard structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal deck with shear studs. Metal deck, beams and columns will include sprayapplied fireproofing.


Configuration

Layout

Scenarios

4a

Lobby

1

Lobby Height [m]

6

Mec. Floors

3


8

Office Floors

115


4

Total Floor Number

119

Height [m]

490

Width [m]

75

Length [m]

50


55


23


40


33


23


79


446,250

Lower Net Area [m2]

99,400

2

Upper Net Area [m ]

236,289

Total Net Area [m2]

335,689

Built Floor Area [m ]

372,543


20


26

2

Columns


0


11,824


146 | Appendix




Concrete

Steel

Other Total Scrap

Property



10 ksi Concrete

76,864

144,744

9 ksi Concrete

0

0

8 ksi Concrete

23,242

29,938

6 ksi Concrete

64,209

0

4-5 ksi Concrete

83,543

83,543

Steel Rebar

7,424

10,683

WWF

764

764

Steel Studs

75

75

Metal Decking

3,563

3,563

Steel Beams

11,861

11,608

Steel Columns

25,923

19,369

Steel Trusses

2,641

5,125

Fireproofing Spray

2,422

2,422


304,952

314,256

Scrap Input

39,944

38,558


51,400

50,217

Net Scrap

11,456

11,659


French EPDs


US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

103,248

1,130,616

114,721

1,207,488

Cradle to Site

106,307

1,186,952

117,780

1,263,824

Cradle to Grave

108,010

1,219,233

119,482

1,296,106

94,033

1,115,316

105,505

1,192,189

Cradle to Cradle



French EPDs GWP [t CO2Eq.]

EE [GJ]

US EPDs GWP [t CO2Eq.]

EE [GJ]

Cradle to Gate

104,497

1,136,533

120,317

1,229,855

Cradle to Site

107,643

1,194,378

123,462

1,287,700

Cradle to Grave

109,405

1,227,723

125,225

1,321,045

95,260

1,123,142

111,079

1,216,464

Cradle to Cradle




Appendix | 147

1.296.106 epds 1.192.189 epds


1.219.233 betie 1.115.316 betie

1.263.824 epds 1.186.952

betie

epds betie

1.263.824

US EPDs Values French Concrete Values

1.186.952

1.130.616 betie

[GJ]

epds

Embodied Energy

1.207.488

Scenario 4a: 120-Story Building – Concrete Core with Steel (Normal Steel) Frame Scenario Structural Firm 01 Graphical Representation of the Research Result

not relevant during the using phase

Years

119.482 108.010 betie

US EPDs Values

epds

epds

70

epds

60

105.505

50

117.780

epds

117.780

20

106.307 betie

epds

535.251

Global Warming Potential

114.721

10


94.033 betie

[tons CO2eq]

106.307 betie

103.248 betie


not relevant during the using phase

60.316

10

20

50

60

Years

70 demolition


scrap recycling

Production of materials

Recycled Input

Life Phase

Construction




148 | Appendix




Demolition

US EPDs French EPDs

-535,251

US EPDs French EPDs

Production Process 1,742,739 1,665,866




Demolition

Credits for Scrap

56,336

N.A.

32,282

103,918

3,059

N.A.

1,702

13,977

175,036 -60,316

163,564


Scenario 4a: 120-Story Building – Concrete Core with Steel (Normal Steel) Frame Scenario Structural Firm 02 Graphical Representation of the Research Result

600.000


1.321.045 epds 1.216.464 epds

epds

1.287.700 betie



1.227.723 betie 1.123.142 betie

900.000

1.194.378

1.136.533 betie

betie

1.200.000

US EPDs Values

1.194.378

epds

1.500.000

1.287.700

1.800.000

epds

[GJ]

1.229.855

Embodied Energy

300.000

10

600.000

20

50

60

Years

70

516.681

300.000

80.000

50

60


epds

epds

125.225

111.079

109.405 betie


95.260 betie

123.462

epds

20

107.643 betie

US EPDs Values French Concrete Values not relevant during the use phase

10 58.223

40.000

epds

40.000

123.462

80.000

107.643 betie

120.000

epds

140.000

120.317

[tons CO2eq]

104.497 betie

180.000

Global Warming160.000 Potential

Years



Life Phase

Construction




US EPDs French EPDs

scenario 4a

-516,681

US EPDs French EPDs




Demolition





Demolition

Credits for Scrap

57,844

N.A.

33,345

104,581

3,146

N.A.

1,762

14,146

178,540 -58,223

162,720


Appendix | 149

Scenario 4b

120-Story Building – Concrete Core with Steel (High Strength Steel) Frame Scenario

Scenario 4b Description • The structure is composed of a reinforced concrete core and standard structural steel profiles (i.e. wide flange I-shapes). • The steel used for the columns is 65 ksi (F450 MPa) high strength steel, while all other structural elements use normal 50 ksi (345 MPa) steel. • Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams are for gravity framing only (not lateral). • Beams are made of standard structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal deck with shear studs. Metal deck, beams and columns will include spray-applied fireproofing.


Configuration

Layout

Scenarios

4b

Lobby

1

Lobby Height [m]

6

Mec. Floors

3


8

Office Floors

115


4

Total Floor Number

119

Height [m]

490

Width [m]

75

Length [m]

50


55


23


40


33


23


79


446,250

Lower Net Area [m2]

99,400

2

Upper Net Area [m ]

236,289

Total Net Area [m2]

335,689


372,543


20


26

2

Columns


0


11,824


150 | Appendix




Concrete

Steel

Other Total Scrap

Property



10 ksi Concrete

76,864

144,744

9 ksi Concrete

0

0

8 ksi Concrete

23,242

29,938

6 ksi Concrete

64,209

0

4-5 ksi Concrete

83,543

83,543

Steel Rebar

7,424

10,683

WWF

764

764

Steel Studs

75

75

French EPDs


US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

103,248

1,130,616

114,721

1,207,488

Cradle to Site

106,307

1,186,952

117,780

1,263,824

Cradle to Grave

108,010

1,219,233

119,482

1,296,106

94,033

1,115,316

105,505

1,192,189

Cradle to Cradle


Table 10.3.4b: Results for Scenario 4b Structural Firm 01 Source: CTBUH Scenario 4b Structural Firm 02

Metal Decking

3,563

3,563

Steel Beams

11,861

11,608

Steel Columns

25,923

16,420

Steel Trusses

2,641

5,125

Fireproofing Spray

2,442

4,844

Cradle to Gate

101,033

1,091,401

116,852

1,184,723

Cradle to Site

104,155

1,148,958

119,974

1,242,280

105,912

1,182,238

121,731

1,275,560

92,394

1,083,224

108,213

1,176,546

LCA Modules


304,952

311,307

Scrap Input

39,944

36,055



51,400

47,297

Net Scrap

11,456

11,243



French EPDs GWP [t CO2Eq.]

EE [GJ]

US EPDs GWP [t CO2Eq.]

EE [GJ]



Appendix | 151

Scenario 4b: 120-Story Building – Concrete Core with Steel (High-Strength Steel) Frame Scenario Structural Firm 01 Graphical Representation of the Research Result

600.000


1.296.106 epds 1.192.189 epds

epds

1.263.824 betie



1.219.233 betie 1.115.316 betie

900.000

1.186.952

1.130.616 betie

betie

1.200.000

US EPDs Values

1.186.952

epds

1.500.000

1.263.824

1.800.000

epds

[GJ]

1.207.488

Embodied Energy

300.000

10

600.000

20

50

60

Years

70

535.251

300.000

80.000

20

50

60

epds

epds

119.482

105.505

108.010 betie

Years

70 demolition



94.033 betie

117.780

epds

10 60.316

40.000


106.307 betie

40.000

117.780

80.000

106.307 betie

epds

120.000

114.721

140.000

103.248 betie

[tons CO2eq]

epds

180.000


scrap recycling


Life Phase

Construction




152 | Appendix




Demolition

US EPDs French EPDs

-535,251

US EPDs French EPDs





Demolition

Credits for Scrap

56,336

N.A.

32,282

103,918

3,059

N.A.

1,702

13,977

175,036 -60,316

163,564


Scenario 4b: 120-Story Building – Concrete Core with Steel (High-Strength Steel) Frame Scenario Structural Firm 02 Graphical Representation of the Research Result

1.275.560 epds 1.176.546 epds

epds

1.242.280



1.182.238 betie 1.083.224 betie

600.000


betie

900.000

1.148.958

1.091.401 betie

betie

1.200.000

US EPDs Values

1.148.958

epds

1.500.000

1.242.280

1.800.000

epds

[GJ]

1.184.723

Embodied Energy

300.000

10

600.000

20

50

60

Years

70

483.131

300.000

80.000

20

50

60


epds

epds

121.731

108.213

105.912 betie

epds

10 54.442

40.000


92.394 betie

40.000

119.974

80.000


104.155 betie

101.033 betie

120.000

104.155 betie

140.000

119.974

epds

116.852

[tons CO2eq]

epds

180.000


Years



Life Phase

Construction


Demolition





structural firm 02


US EPDs French EPDs

-483,131

US EPDs French EPDs




Demolition

Credits for Scrap

57,557

N.A.

33,280

99,014

3,122

N.A.

1,757

13,518

171,295 -54,442

155,476


Appendix | 153

Scenario 4c

120-Story Building – Concrete Core and Compostie Frame Scenario

Scenario 4c Description • The structure is composed of a concrete core with composite steel/concrete columns on the perimeter. • The columns use standard structural steel sections with 50 ksi (34 MPa) strength as their core, covered with high strength 8-10 ksi (60-70 MPa) reinforced concrete. • Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams are for gravity framing only (not lateral). • Beams are made of standard structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal deck with shear studs. Metal deck, beams and columns will include sprayapplied fireproofing.


Configuration

Layout

Scenarios

4c

Lobby

1

Lobby Height [m]

6

Mec. Floors

3


8

Office Floors

115


4

Total Floor Number

119

Height [m]

490

Width [m]

75

Length [m]

50


55


23


40


33


23


79


446,250

Lower Net Area [m2]

99,400

2

Upper Net Area [m ]

236,289

Total Net Area [m2]

335,689


372,543


20


26

2

Columns


0


11,824


154 | Appendix




Concrete

Steel

Property



10 ksi Concrete

85,130

179,399

9 ksi Concrete

0

0

8 ksi Concrete

32,563

38,511

6 ksi Concrete

81,793

0

4-5 ksi Concrete

83,543

83,543

Steel Rebar

8,028

10,560

WWF

764

764

Steel Studs

75

75

Metal Decking

3,563

3,563

Steel Beams

11,861

11,608

Steel Columns

5,526

3,538

French EPDs

LCA Modules

US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

Cradle to Gate

85,569

869,740

98,334

954,722

Cradle to Site

88,511

926,235

101,276

1,011,216

Cradle to Grave

90,417

961,564

103,182

1,046,546

81,009

900,964

93,774

985,945

Cradle to Cradle


Table 10.3.4c Results for Scenario 4c Structural Firm 01 Source: CTBUH


US EPDs

Steel Trusses

2,641

0

LCA Modules

Other

Fireproofing Spray

2,351

2,351

Cradle to Gate

92,580

943,434

111,429

1,051,636

Total


320,189

341,253

Cradle to Site

95,626

1,001,996

114,475

1,110,198

Scrap Input

23,048

24,917

Cradle to Grave

97,642

1,039,256

116,491

1,147,458


31,781

34,294

87,504

973,652

106,353

1,081,854

Scrap

Cradle to Cradle


Net Scrap


8,732

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

9,376



Appendix | 155


Embodied Energy

[GJ]

600.000

epds

French Concrete Values not relevant during the use phase

10

20

50

60


Years

70

308.847

300.000

1.046.546 epds 985.945 epds

300.000

961.564 betie 900.964 betie

869.740 betie

600.000

US EPDs Values

926.235 betie

900.000

1.011.216

1.200.000

926.235 betie

954.722

1.500.000

1.011.216

epds

epds

1.800.000

40.000

10

34.803

20

50

60

103.182 epds

93.774 epds

betie

Years

70 demolition


80.000

90.417

40.000



81.009 betie

85.569 betie

80.000

US EPDs Values

101.276 epds

120.000

88.511 betie

98.334

140.000

88.511 betie

epds

[tons CO2eq]

101.276 epds

180.000


scrap recycling


Life Phase

Construction




156 | Appendix




Demolition

US EPDs French EPDs

-308,847

US EPDs French EPDs





Demolition

Credits for Scrap

56,494

N.A.

35,330

60,601

2,942

N.A.

1,906

9,408

133,137 -34,803

120,372



Embodied Energy 1.147.458 epds 1.081.854 epds 1.039.256 betie 973.652 betie

epds

1.110.198

600.000

1.001.996 betie

epds

943.434 betie

900.000

1.110.198

1.200.000


1.001.996 betie

1.500.000

epds

1.800.000

1.051.636

[GJ]



300.000

600.000

10

20

50

60

Years

70

333.892

300.000

40.000

10

37.625

20

50

60


80.000

116.491 epds

106.353 epds

betie

97.642

40.000



87.504 betie

92.580 betie

80.000

US EPDs Values

114.475 epds

120.000

95.626 betie

140.000

95.626 betie

111.429 epds

[tons CO2eq]

114.475 epds

180.000


Years



Life Phase

Construction


Demolition





structural firm 02


US EPDs French EPDs

-333,892

US EPDs French EPDs




Demolition

Credits for Scrap

58,562

N.A.

37,260

65,604

3,046

N.A.

2,016

10,137

149,054 -37,625

130,205


Appendix | 157

Scenario 5a

120-Story Building – All Concrete with Wide and Shallow Beams Scenario

Scenario 5a Description • The structure is composed of a concrete core with concrete columns on the perimeter. The floor system is composed of a concrete slab with wide and shallow concrete beams. • Multiple grades of concrete from 4 ksi (30 MPa) to 10 ksi (70 MPa) are used for different structural components. The lightweight 4-5 ksi is used for floors, while the higher grades (6 ksi and up) are used for the lateral elements. All reinforcements are also made of normal 50 ksi (340 MPa) steel. • 220 mm rebar slab with PT/rebar band beams 2000 mm wide and 450 mm deep at 9 m off-center are used to match column lines. • Beams and floors are made of 4-5 ksi (30-37 MPa) with normal 50 ksi steel. • Disposable wooden formwork is considered beneath all the floors and beams.


Configuration

Layout

Scenarios

5a

Lobby

1

Lobby Height [m]

6

Mec. Floors

3


8

Office Floors

115


4

Total Floor Number

119

Height [m]

490

Width [m]

75

Length [m]

50


55


23


40


33


23


79


446,250

Lower Net Area [m2]

99,400

2

Upper Net Area [m ]

236,289

Total Net Area [m2]

335,689


372,543


20


26

2

Columns


0


11,824


158 | Appendix



Concrete

Steel


Property



10 ksi Concrete

104,871

139,518

9 ksi Concrete

0

0

8 ksi Concrete

65,368

82,184

6 ksi Concrete

40,242

49,981

4-5 ksi Concrete

237,496

237,496

Steel Rebar

17,064

20,399

WWF

764

764

Steel Studs

0

0

Metal Decking

0

0

Steel Beams

0

0

Steel Columns

0

0

French EPDs

LCA Modules

US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

Cradle to Gate

82,237

745,752

102,892

899,305

Cradle to Site

84,435

796,798

105,091

950,351

Cradle to Grave

87,190

847,854

107,845

1,001,407

86,286

875,454

106,942

1,029,007

Cradle to Cradle



Scenario 5a Structural Firm 02 French EPDs

US EPDs

Steel Trusses

0

0

LCA Modules

Other

Fireproofing Spray

0

0

Cradle to Gate

96,248

875,061

120,375

1,047,027

Total


465,805

530,341

Cradle to Site

98,611

930,803

122,737

1,102,769

Scrap Input

12,443

14,771

Cradle to Grave

101,714

988,060

125,841

1,160,026


16,936

20,104

100,346

1,016,402

124,472

1,188,368

Scrap

Cradle to Cradle


Net Scrap


4,492

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

5,333



Appendix | 159


Embodied Energy

[GJ]

900.000

10

166.741

300.000

300.000

betie


20

796.798

600.000

796.798

745.752 betie

betie


50

60

1.001.407 epds 1.029.007 epds

US EPDs Values


847.854 betie 875.454 betie

epds

950.351

epds

950.351

1.200.000

epds

1.500.000

899.305

1.800.000

Years

70

600.000

107.845 epds

106.942 epds

betie

86.286 betie


82.237 betie


10

18.789

40.000

84.435 betie


80.000

40.000

US EPDs Values

87.190

120.000

105.091 epds

140.000

84.435 betie

102.892 epds

[tons CO2eq]

105.091 epds

180.000


20

50

60


80.000

Years



Life Phase

Construction




160 | Appendix




Demolition

US EPDs French EPDs

-166,741

US EPDs French EPDs

Production Process 1,066,046 912,493




Demolition

Credits for Scrap

51,046

N.A.

51,056

-27,600

2,199

N.A.

2,755

903

121,681 -18,789

101,026



Embodied Energy 1.160.026 epds 1.188.368 epds

epds

1.200.000

1.102.769

1.500.000

epds

1.047.027 epds

1.800.000

1.102.769

[GJ]

300.000

betie

930.803

betie


10

197.935

300.000

930.803

875.061 betie

600.000


20

50

60

988.060 betie 1.016.402 betie

US EPDs Values 900.000


Years

70

600.000

125.841 epds

124.472 epds


20

50

60


80.000

101.714

98.611 betie


10

22.305

40.000

98.611 betie

96.248 betie


80.000

40.000

US EPDs Values

betie

120.000

100.346 betie

140.000

122.737 epds

120.375 epds

[tons CO2eq]

122.737 epds

180.000


Years



Life Phase

Construction




US EPDs French EPDs

scenario 5a

-197,935

US EPDs French EPDs




Demolition





Demolition

Credits for Scrap

55,742

N.A.

57,257

-28,342

2,363

N.A.

3,103

1,369

142,679 -22,305

118,553


Appendix | 161

Scenario 5b

120-Story Building – All Concrete with Narrow and Deep Beams Scenario

Scenario 5b Description • The structure is composed of a concrete core with concrete columns on the perimeter. The floor system is composed of a concrete slab with narrow and deep concrete beams. • Multiple grades of concrete from 4 ksi (30 MPa) to 10 ksi (70 MPa) are used for different structural components. The lightweight 4-5 ksi is used for floors, while the higher grades (6 ksi and up) are used for the lateral elements. All reinforcements are also made of normal 50 ksi (340 MPa) steel. • Beams 150 mm rebar slab with PT/rebar beams 400 mm wide and 450 mm deep at 3 m off-center (assume pinned moment connection at core and perimeter for gravity system beam framing). • Beams and floors are made of 4-5 ksi (30-37 MPa) with normal 50 ksi steel. • Disposable wooden formwork is considered beneath all the floors and beams.


Configuration

Layout

Scenarios

5b

Lobby

1

Lobby Height [m]

6

Mec. Floors

3


8

Office Floors

115


4

Total Floor Number

119

Height [m]

490

Width [m]

75

Length [m]

50


55


23


40


33


23


79


446,250

Lower Net Area [m2]

99,400

2

Upper Net Area [m ]

236,289

Total Net Area [m2]

335,689


372,543


20


26

2

Columns


0


11,824


162 | Appendix




Concrete

Steel

Property



10 ksi Concrete

104,871

139,518

9 ksi Concrete

0

0

8 ksi Concrete

65,368

82,184

6 ksi Concrete

40,242

49,981

4-5 ksi Concrete

173,232

173,232

Steel Rebar

16,915

21,330

WWF

764

764

Steel Studs

0

0

Metal Decking

0

0

Steel Beams

0

0

Steel Columns

0

0

French EPDs

LCA Modules

US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

Cradle to Gate

74,982

689,966

93,067

818,456

Cradle to Site

77,126

737,493

95,211

865,983

Cradle to Grave

79,525

782,172

97,610

910,662

77,836

797,704

95,921

926,194

Cradle to Cradle




US EPDs

Steel Trusses

0

0

LCA Modules

Other

Fireproofing Spray

0

0

Cradle to Gate

90,338

837,016

111,894

983,920

Total


401,392

467,008

Cradle to Site

92,683

889,693

114,239

1,036,597

Scrap Input

12,339

15,421

Cradle to Grave

95,435

940,617

116,991

1,087,520


16,794

20,989

92,871

953,253

114,426

1,100,156

Scrap

Cradle to Cradle


Net Scrap


4,455

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

5,568



Appendix | 163

Scenario 5b: 120-Story Building – All Concrete with Narrow and Deep Beams Scenario Structural Firm 01 Graphical Representation of the Research Result

Embodied Energy

[GJ]

10

165,347

300.000

20

50

60

910.662 epds 926.194 epds betie

betie


782.172 797.704

865.983 betie


737.493

betie

300.000

betie

600.000

689.966

900.000


737.493

1.200.000

865.983

818.456 epds

epds

1.500.000

epds

1.800.000

Years

70

600.000

180.000

40.000

18.632

10

20

50

60


80.000

epds

95.921 epds

97.610 betie


77.836 betie

40.000

79.525

80.000

95.211 epds


77.126 betie

epds

95.211 77.126 betie

120.000

epds

140.000

93.067

[tons CO2eq]

74.982 betie


Years



Life Phase

Construction




164 | Appendix




Demolition

US EPDs French EPDs

-165,347

US EPDs French EPDs





Demolition

Credits for Scrap

47,527

N.A.

44,679

-15,532

2,144

N.A.

2,399

1,689

111,699 -18,632

93,615


Scenario 5b: 120-Story Building – All Concrete with Narrow and Deep Beams Scenario Structural Firm 02 Graphical Representation of the Research Result

Embodied Energy

[GJ]

300.000

betie

10

206.646

300.000


889.693

betie

837.016

600.000

betie

900.000

20

50

60

1.087.520 epds 1.100.156 epds


940.617 betie 953.253 betie


889.693

1.200.000

1.036.597

1.036.597 epds

epds

983.920

1.500.000

epds

1.800.000

Years

70

600.000

40.000

23.286

10

20

50

60


80.000

116.991 epds

114.426 epds

betie

95.435

92.871 betie


114.239 epds


92.683 betie

40.000

114.239

80.000

92.683 betie

120.000

111.894 epds

140.000

90.338 betie

[tons CO2eq]

epds

180.000



Years



Life Phase

Construction


Demolition





structural firm 02


US EPDs French EPDs

-206,646

US EPDs French EPDs




Demolition

Credits for Scrap

52,677

N.A.

50,923

-12,636

2,345

N.A.

2,751

2,564

135,180 -23,286

113,624


Appendix | 165

Scenario 6a

120-Story Building – All Steel (Normal Steel) Diagrid Scenario

Scenario 6a_Description • The structure is composed of a diagrid of standard structural steel profiles. Core columns carry vertical loads only. In case of inadequate stiffness, concrete core and outriggers (at the service floor levels) can be added. • The steel used for all structural elements is normal 50 ksi (345 Mpa) steel. • Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams are for gravity framing only (not lateral). • Beams are made of standard structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal deck with shear studs. Metal deck, beams and columns will include spray applied fireproofing.


Configuration

Layout

Columns

Additional Remarks: NOTE

As evidenced in this study, an all diagrid solution loses efficiency when the tower becomes too slender (i.e., the short direction of a rectangular floor plate). Diagrid tubes have been shown to be most effective on their own when the tower’s proportions are square. This finding points to the need for designers to exercise appropriate judgment when initially selecting building systems.

166 | Appendix

6a

Scenarios

S.F. 01

S.F. 02

Lobby

1

0

Lobby Height [m]

6

6

Mec. Floors

3

3


8

8

Office Floors

115

115


4

4

Total Floor Number

119

119

Height [m]

490

490

Width [m]

75

75

Length [m]

50

50


55

55


23

23


40

40


33

33


23

23


79

79


446,250

446,250

Lower Net Area [m2]

99,400

99,400

Upper Net Area [m2]

236,289

236,289

Total Net Area [m2]

335,689

335,689


372,543

372,543


24

*


0

6

Number of diagrid Columns

60

60


48,510

38,670

Structural firm #2 decided to have a concrete core in the diagrid system so there are only 6 columns supporting the floors in the upper portion of the building where the core steps back. Check for structural concrete.




Concrete

Steel

Other Total Scrap


Property



10 ksi Concrete

0

116,667

9 ksi Concrete

0

71,029

8 ksi Concrete

0

41,765

6 ksi Concrete

0

0

4-5 ksi Concrete

83,543

83,543

Steel Rebar

1,611

9,991

WWF

764

764

Steel Studs

75

75

Metal Decking

3,563

3,563

Steel Beams

18,062

11,147

French EPDs

LCA Modules

GWP [t CO2Eq.]

EE [GJ]

US EPDs EE [GJ]

GWP [t CO2Eq.]

Cradle to Gate

124,594

1,542,438

127,936

1,575,020

Cradle to Site

129,526

1,620,953

132,868

1,653,535

Cradle to Grave

130,250

1,637,140

133,592

1,669,722

105,907

1,428,242

109,248

1,460,823

Cradle to Cradle


Table 10.3.6a Results for Scenario 6a Structural Firm 01 Source: CTBUH Scenario 6a Structural Firm 02 LCA Modules

French EPDs

US EPDs

Steel Columns

14,850

784

Steel Trusses

54,900

29,719

Fireproofing Spray

2,642

2,583

Cradle to Gate

118,259

1,265,348

137,869

1,377,401

Cradle to Site

123,287

1,355,235

142,898

1,467,287

125,222

1,393,478

144,832

1,505,531

110,906

1,291,760

130,516

1,403,813


182,652

374,213

Scrap Input

75,890

42,803



92,791

55,052

Net Scrap

16,901

12,250



GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]



Appendix | 167

900.000

1.669.722 epds 1.460.823 epds betie

epds

1.653.535 betie



1.637.140 1.428.242 betie

1.200.000

US EPDs Values

1.620.953

1.500.000

1.653.535 epds

1.800.000

1.620.953 betie

[GJ]

1.575.020 epds

Embodied Energy

1.542.438 betie



600.000 300.000

10

300.000

20

50

60

Years

70

1.016.929

600.000

10

80.000

114.594

40.000

20

50

60

133.592 epds

109.248 epds

130.250 betie


40.000

Years

70 demolition



105.907 betie

80.000


132.868 epds

124.594 betie

120.000

129.526 betie

140.000

129.526 betie

127.936 epds

[tons CO2eq]

132.868 epds

180.000


scrap recycling

Production of materials

Recycled Input

Life Phase

Construction




168 | Appendix




Demolition

US EPDs French EPDs

-1,016,929

US EPDs French EPDs





Demolition

Credits for Scrap

78,515

N.A.

16,187

208,899

4,932

N.A.

724

24,344

242,530 -114,594

239,188


900.000 600.000


1.505.531 epds 1.403.813 epds

1.467.287



1.393.478 betie 1.291.760 betie

1.200.000

betie

1.265.348 betie

1.500.000

US EPDs Values

1.355.235

1.800.000

1.467.287 epds

[GJ]

1.355.235 betie

1.377.401 epds

Embodied Energy

epds


300.000

10

600.000

20

50

60

Years

70

573.557

300.000

40.000

80.000

10 64.632

40.000

20

50

60


144.832 epds

130.516 epds

125.222 betie



110.906 betie

80.000


142.898 epds

118.259 betie

120.000

US EPDs Values

123.287 betie

140.000

123.287 betie

137.869 epds

[tons CO2eq]

142.898 epds

180.000


Years



Life Phase

Construction


Demolition





structural firm 02


US EPDs French EPDs

-573,557

US EPDs French EPDs




Demolition

Credits for Scrap

89,887

N.A.

38,243

101,718

5,029

N.A.

1,934

14,316

202,501 -64,632

182,891


Appendix | 169

Scenario 6b

120-Story Building – All Steel (High Strength Steel) Diagrid Scenario

Scenario 6b Description • The structure is composed of a diagrid of standard structural steel profiles. Core columns carry vertical loads only. In case of inadequate stiffness, concrete core and outriggers (at the service floor levels) can be added. • The steel used for the columns is 65 ksi (F450 Mpa) high strength steel, while beams and diagrid braces use normal 50 ksi (345 Mpa) steel. • Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams are for gravity framing only (not lateral). • Beams are made of standard structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal deck with shear studs. Metal deck, beams and columns will include spray-applied fireproofing.


Configuration

Layout

Columns

Additional Remarks: NOTE

As evidenced in this study, an all diagrid solution loses efficiency when the tower becomes too slender (i.e., the short direction of a rectangular floor plate). Diagrid tubes have been shown to be most effective on their own when the tower’s proportions are square. This finding points to the need for designers to exercise appropriate judgment when initially selecting building systems.

170 | Appendix

6b

Scenarios

S.F. 02 Lobby

1

1

Lobby Height [m]

6

6

Mec. Floors

3

3


8

8

Office Floors

115

115


4

4

Total Floor Number

119

119

Height [m]

490

490

Width [m]

75

75

Length [m]

50

50


55

55


23

23


40

40


33

33


23

23


79

79


446,250

446,250

Lower Net Area [m2]

99,400

99,400

Upper Net Area [m2]

236,289

236,289

Total Net Area [m2]

335,689

335,689


372,543

372,543


24

*


0

6

Number of diagrid Columns

60

60


48,510

38,670

Structural firm #2 decided to have a concrete core in the diagrid system so there are only 6 columns supporting the floors in the upper portion of the building where the core steps back. Check for structural concrete.





Concrete

Steel

Property



10 ksi Concrete

0

116,667

9 ksi Concrete

0

71,029

8 ksi Concrete

0

41,765

6 ksi Concrete

0

0

4-5 ksi Concrete

83,543

83,543

Steel Rebar

1,611

9,991

WWF

764

764

Steel Studs

75

75

Metal Decking

3,563

3,563

Steel Beams

18,062

11,147

Steel Columns

11,700

784

French EPDs

LCA Modules

US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

Cradle to Gate

120,894

1,494,230

124,236

1,526,811

Cradle to Site

125,801

1,572,438

129,142

1,605,019

Cradle to Grave

126,519

1,588,556

129,860

1,621,137

102,845

1,385,602

106,187

1,418,184

Cradle to Cradle




US EPDs

Steel Trusses

54,900

29,719

LCA Modules

Other

Fireproofing Spray

2,642

2,583

Cradle to Gate

118,259

1,265,348

137,869

1,377,401

Total


179,502

374,213

Cradle to Site

123,287

1,355,235

142,898

1,467,287

Scrap Input

73,216

42,803

Cradle to Grave

125,222

1,393,478

144,832

1,505,531


89,673

55,052

110,906

1,291,760

130,516

1,403,813

Scrap

Cradle to Cradle


Net Scrap


16,457

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

12,250



Appendix | 171

1.200.000 900.000

epds

1.605.019


1.588.556 betie 1.621.137 epds 1.385.602 betie 1.418.184 epds

1.494.230 betie

1.500.000

US EPDs Values

betie

1.800.000

1.572.438

[GJ]

1.572.438 betie

1.526.811 epds

Embodied Energy

1.605.019 epds

Scenario 6b: 120-Story Building – All Steel (High Strength Steel) Diagrid Scenario Structural Firm 01 Graphical Representation of the Research Result



600.000 300.000

10

300.000

20

50

60

Years

70

981.093

600.000

80.000 40.000


10 110.556

40.000 80.000


20

50

60

106.187 epds

126.519 betie 129.860 epds

120.894 betie

120.000

US EPDs Values

Years

70 demolition



102.845 betie

140.000

125.801 betie 129.142 epds

124.236 epds

[tons CO2eq]

125.801 betie 129.142 epds

180.000


scrap recycling


Life Phase

Construction




172 | Appendix




Demolition

US EPDs French EPDs

-981,093

US EPDs French EPDs





Demolition

Credits for Scrap

78,208

N.A.

16,118

202,953

4,907

N.A.

718

23,673

234,792 -110,556

231,450


900.000 600.000


1.505.531 epds 1.403.813 epds

1.467.287



1.393.478 betie 1.291.760 betie

1.200.000

betie

1.265.348 betie

1.500.000

US EPDs Values

1.355.235

1.800.000

1.467.287 epds

[GJ]

1.355.235 betie

1.377.401 epds

Embodied Energy

epds

Scenario 6b: 120-Story Building – All Steel (High Strength Steel) Diagrid Scenario Structural Firm 02 Graphical Representation of the Research Result

300.000

10

600.000

20

50

60

Years

70

573.557

300.000

10 64.632

40.000 80.000

20

50

60


130.516 epds

144.832 epds


125.222 betie

40.000


110.906 betie

80.000


142.898 epds

118.259 betie

120.000

US EPDs Values

123.287 betie

140.000

123.287 betie

137.869 epds

[tons CO2eq]

142.898 epds

180.000


Years



Life Phase

Construction




US EPDs French EPDs

scenario 6b

-573,557

US EPDs French EPDs




Demolition





Demolition

Credits for Scrap

89,887

N.A.

38,243

101,718

5,029

N.A.

1,934

14,316

202,501 -64,632

182,891


Appendix | 173

Scenario 6c

120-Story Building – Composite Diagrid Scenario

Scenario 6c Description • The structure is composed of a diagrid of composite steel/concrete members. In case of inadequate stiffness, concrete core and outriggers (at the service floor levels) can be added. • The columns and braces (all composite) are standard structural steel sections with 50 ksi (345 Mpa) strength as their core, covered with high strength 8-10 ksi (60-70 MPa) reinforced concrete. • Steel beams at 3 m off-center, spanning core to exterior. Perimeter edge beams are for gravity framing only (not lateral). • Beams are composed of standard shape structural steel profiles. • Floors consist of 65 mm normal weight concrete over 75 mm, 20 ga system metal deck with shear studs. Metal deck, beams and columns will include spray applied fireproofing.


Configuration

Layout

Columns

Additional Remarks: A composite concrete and steel diagrid on the building perimeter, which creates a “tube,” resulted (on average) in the best solution for the 120-story building, as all overturning is carried on the exterior. The tube’s efficiency was challenged in the narrow direction, though, and required supplemental stiffening to make it most effective.

6c

Scenarios

NOTE

S.F. 01

S.F. 02

Lobby

1

1

Lobby Height [m]

6

6

Mec. Floors

3

3


8

8

Office Floors

115

115


4

4

Total Floor Number

119

119

Height [m]

490

490

Width [m]

75

75

Length [m]

50

50


55

55


23

23


40

40


33

33


23

23


79

79


446,250

446,250

Lower Net Area [m2]

99,400

99,400

Upper Net Area [m2]

236,289

236,289

Total Net Area [m2]

335,689

335,689


372,543

372,543


*

**


8

6


60

60


39,310

38,670

*Structural firm #1 decided to have a concrete core in the composite diagrid system only, so there are only 6 columns supporting the floors in the upper portion of the building where the core steps back. Check for structural concrete **Structural firm #2 decided to have a concrete core in the diagrid system so there are only 6 columns supporting the floors in the upper portion of the building where the core steps back. Check for structural concrete.


174 | Appendix



Concrete

Steel


Property



10 ksi Concrete

56,925

55,306

9 ksi Concrete

0

24,724

8 ksi Concrete

31,050

17,281

6 ksi Concrete

37,261

32,799

4-5 ksi Concrete

83,543

83,543

Steel Rebar

7,911

5,620

WWF

764

764

Steel Studs

75

75

Metal Decking

3,563

3,563

Steel Beams

18,062

10,952

Steel Columns

0

648

French EPDs

LCA Modules

US EPDs

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

Cradle to Gate

81,929

882,647

91,501

949,705

Cradle to Site

84,863

935,740

94,435

1,002,798

Cradle to Grave

86,208

965,166

95,780

1,032,224

74,126

874,949

83,698

942,007

Cradle to Cradle




US EPDs

Steel Trusses

8,550

21,138

LCA Modules

Other

Fireproofing Spray

2,351

2,351

Cradle to Gate

86,092

934,628

97,011

1,006,216

Total


252,406

261,114

Cradle to Site

88,999

987,616

99,918

1,059,203

Scrap Input

28,329

32,192

Cradle to Grave

90,375

1,017,568

101,294

1,089,156


38,188

42,077

78,319

927,962

89,238

999,550

Scrap

Cradle to Cradle


Net Scrap


9,860

GWP [t CO2Eq.]

EE [GJ]

GWP [t CO2Eq.]

EE [GJ]

9,884



Appendix | 175


Embodied Energy

[GJ]


10

20

50

60


Years

70

379.606

300.000

1.032.224 epds 942.007 epds

300.000

965.166 betie 874.949 betie

1.002.798 935.740 betie

600.000

epds

949.705

900.000

1.002.798

epds

1.200.000

935.740 betie

1.500.000

882.647 betie

epds

1.800.000

600.000

180.000

40.000

20

50

60


80.000

95.780 epds

83.698

betie

86.208


74.126 betie

94.435 epds


betie


10

42.777

40.000

US EPDs Values

84.863

81.929 betie

80.000

betie

120.000

84.863

91.501 epds

140.000

94.435 epds

[tons CO2eq]

epds


Years



Life Phase

Construction



"Global Warming Potential" [tCO2Eq.]

176 | Appendix



Benefits of Using Recycled Inputs "Embodied Energy" [GJ]

Demolition

US EPDS French EPDS

-379,606

US EPDS French EPDS

"Production Process" 1,329,311 1,262,253




Demolition

Credits for Scrap

53,093

N.A.

29,427

90,217

2,934

N.A.

1,345

12,082

134,278 -42,777

124,705



Embodied Energy

[GJ]

600.000

1.089.156 epds 999.550 epds 1.017.568 betie 927.962 betie


10

20

50

60


Years

70

431.377

300.000

epds

300.000

1.059.203

600.000

987.616 betie

934.628 betie

900.000

epds

1.200.000

1.059.203

1.500.000

987.616 betie

1.006.216 epds

1.800.000

180.000

40.000

20

50

60


80.000

epds

101.294 epds

89.238

betie

90.375


78.319 betie

99.918 epds


10

48.610

40.000


88.999

86.092 betie

80.000

betie

120.000

betie

97.011 epds

140.000

88.999

[tons CO2eq]

99.918 epds


Years



Life Phase

Construction


Demolition





structural firm 02

Benefits of Using Recycled Inputs "Embodied Energy" [GJ] "Global Warming Potential" [tCO2Eq.]

US EPDS French EPDS

-431,377

US EPDS French EPDS

"Production Process" 1,437,593 1,366,005



Demolition

Credits for Scrap

52,988

N.A.

29,953

89,606

2,907

N.A.

1,376

12,056

145,621 -48,610

134,703


Appendix | 177

Acknowledgements

This publication presents the results of a three-year-long research project sponsored by ArcelorMittal. The authors would like to recognize the work and support of the whole research team, including: Payam Bahrami (CTBUH), Martina Belmonte (CTBUH/Iuav), Donald Davies (Magnusson Klemencic Associates), Jean-Claude Gerardy (ArcelorMittal), Eleonora Lucchese (CTBUH/Iuav), Mattia Mercanzin (CTBUH/Iuav), Nicoleta Popa (ArcelorMittal), Meysam Tabibzadeh (CTBUH), Dario Trabucco (CTBUH/Iuav, Principal Investigator), Olivier Vassart (ArcelorMittal), and Antony Wood (CTBUH, Co-Principal Investigator). A large group of firms and professionals contributed to the research by providing specific information that was used in various parts of the research to populate the bill of quantities for the various scenarios, the characterization factors, etc.: Engineering Firms: Arup, Buro Happold, Halvorson & Partners, Magnusson Klemencic Associates, McNamara/Salvia, Nishkian Menninger, Severud Associates, SOM, Thornton Tomasetti, Walter P Moore, Weidlinger Associates, WSP; Demolition Contractors and C&D Waste Processing Plants: ACM Recycling, Bluff City Materials, Brandenburg, Despe, MBL Recycling, Taisei; Construction Companies and Material Providers: Clark Construction, Gerdau Ameristeel, Grace, Putzmeister, Schnell, Terex Group.

178 | Acknowledgements


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Cowlard, A., Bittern, A., Abecassis-Empis, C. & Torero, J. (2013) “Fire Safety Design for Tall Buildings”, Procedia Engineering, Volume 62, 2013, Pages 169–181, 9th Asia-Oceania Symposium on Fire Science and Technology.. Davis, J. et al. (2007). “Time-dependent material flow analysis of iron and steel in the UK: Part 2. Scrap generation and recycling”. Resources, Conservation and Recycling, July, Volume 51(1), pp. 118-140. Dixit, M. K., Fernandèz-Solìs, J. L., Lavy, S. & Culp, C. H. (2012) “Need for an embodied energy measurement protocol for buildings: a review paper”. Renewable and Sustainable Energy Reviews, Volume 16, pp. 3730-3743. Doering, B., Kendrick, C. & Lawson, R. M. (2013) “Thermal capacity of composite floor slabs”, Energy and Buildings, December, Volume 67, pp. 531-539. Elicott, G. (2004) “Structural steel fire protection”, Fire Prevention & Fire Engineers Journal, Jan. pp. 59-61.

Buyle, M., Braet, J. & Audenaert, A. (2013) “Life cycle assessment in the construction sector: A review”. Renewable and Sustainable Energy Reviews, October, Volume 26, pp. 379-388.

Fay, R., Treloar, G. & Iyer-Raniga, U. (2000) “Lifecycle energy analysis of buildings: a case study”. Building Research & Information, Volume 28, pp. 31-41.

Cabeza, L. F. et al. (2014) “Life Cycle Assessment (LCA) and Life Cycle Energy Analysis (LCEA) of Buildings and the building sector: a review”. Renewable and Sustainable Energy Reviews, Volume 29, pp. 394-416.

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Chambers, N. (2014) “Is Net-Zero Tall Possible?”, CTBUH Journal, Volume II.

Galbenis, C.-T. & Tsimas, S. (2006) “Use of Construction and Demolition Wastes as Raw Materials in Cement Clinker Production”, China Particuology, Volume 6, pp. 83-85.

Chan, W. & Wu, C. (2000) “Durability of concrete with high cement replacement”. Cement and Concrete Research, Volume 30(6), pp. 865-879. Cheng, J. C. & Ma, L. Y. (2013) “A BIM-based system for demolition and renovation waste estimation and planning”, Waste Management, Volume 33, pp. 1539-1551.

Gangolells, M. et al. (2009) “A methodology for predicting the severity of environmental impacts related to the construction process of residential buildings”, Building and Environment, Volume 44, pp. 558-571.


Gangolells, M. et al. (2011) “Assessing concerns of interested parties when predicting the significance of environmental impact related to the construction process of residential buildings”, Building and Environment, Volume 46, pp. 1023-1037.

Guggemos, A. et al. (2010) “Greening Structural Steel Design, Fabrication and Erection: A Case Study of the National Renewable Energy” Laboratory Research Support Facilities Project, Fort Collins, CO: Colorado State University. Hajibabai, L., Aziz, Z. & Pena-Mora, F. (2011) “Visualizing greenhouse gas emissions from construction activities”, Construction Innovation, Volume 11(3), pp. 356-370.

Galbenis, C.-T. & Tsimas, S. (2006) “Use of Construction and Demolition Wastes as Raw Materials in Cement Clinker Production”, China Particuology, Volume 6, pp. 83-85.

Hasan, S. et al. (2013) “Productivity and CO2 emission analysis for tower crane utilization on high-rise building projects”,Automation in Construction, Volume 31, pp. 255-264.

Gangolells, M. et al. (2009) “A methodology for predicting the severity of environmental impacts related to the construction process of residential buildings”, Building and Environment, Volume 44, pp. 558-571.

Hong, T., Yoon, C., Jang, M. & Park, H. (2014) “Assessment Model for Energy Consumption and Greenhous Gas Emission during Building Construction”, Journal of Management in Engineering, march/april, pp. 226-235.

Gangolells, M. et al. (2011) “Assessing concerns of interested parties when predicting the significance of environmental impact related to the construction process of residential buildings”, Building and Environment, Volume 46, pp. 1023-1037. Gilsanz, R. (2008) “Reconsidering Fire Resistance Requirements for Tall Buildings” [Online] Available at: http://www.structuremag.org/ wp-content/uploads/2014/08/C-StructuralPractices-Gilsanz-Feb-081.pdf [Accessed Feb. 2015]. Goldenberg, M. & Shapira, A. (2007) “Systematic Evaluation of Construction Equipment Alternatives: Case Study”, Journal of Construction Engineering and Management, ASCE, Jan. 2007, pp. 72-85. Goode, M. G. (2004). “Fire Protection of Structural Steel in High-Rise Buildings” [Online] Available at: http://www.fire.nist.gov/bfrlpubs/ build04/PDF/b04047.pdf [Accessed 09 Feb 2015]. Guggemos, A. A. & Horvath, A. (2005) “Comparison of Environmental Effects of Steeland Concrete-Framed Buildings”, Journal of Infrastructure Systems, ASCE, Volume 11(2), pages 93-101, Guggemos, A. A. & Horvath, A. (2006) “Decision support tool for environmental analysis of commercial building structures”, Journal of Architectural Engineering, Dec.12(4).

Huang, C., Wong, C. & Tam , C. M. (2011) “Optimization of tower crane and material supply locations in a high-rise building site by mixed-integer linear programming”, Automation in Construction, Volume20(5) Aug., pp. 571-580. Hudson, J., (1993) “Excavation, Support and Monitoring”, in “Comprehensive Rock Engineering: Principles, Practice & Projects” pp. 1-37. Hu, M., Kleijn, R., Bozhilova, K. P. & Di Maio, F. (2013) “An approach to LCSA: the case of concrete recycling”, Volume 18(9), June 2013, pp. 1793-1803. Kim, K., Shin, M. & Cha, S. (2013) “Combined effects of recycled aggregate and fly ash towards concrete sustainability”, Construction and Building Materials, Volume 48, pp. 499-507. Knoeri, C., Binder, C. & Althaus, H.-J. (2011) “Decisions on recycling: Construction stakeholders’ decisions regarding recycled mineral construction materials”, Resources, Conservation and Recycling, Volume 55, pp. 1039-1050. Kofoworola, O. F. & Gheewala, S. H., (2009) “Life Cycle Assessment of a typical office building in Thailand”, Energy and Buildings, Volume 41, pp. 1076-1083.

Lenzen, S. et al. (2004) “System Boundary Selection in Life-Cycle Inventories Using Hybrid Approaches”, Environmental Science & Technology, Volume 38(3), pp. 657-664. Leslie, T. (2013) “The Monadnock Building, Technically Reconsidered”. CTBUH Journal, Volume Issue IV. Li, X., Zhu, Y. & Zhang, Z. (2010). “A LCA-based environmental impact assessment model for construction processes”, Building and Environment, March, Volume 45(3), pp. 766-775. Marinkovic’, A., Radonjanin, V., Malešev, M. & Ignjatovic’, I. (2010) “Comparative environmental assessment of natural and recycled aggregate concrete”, Waste Management, Volume 30, pp. 2255-2264. Martínez, E., Nuñez, Y. & Sobaberas, E. (2013) “End of life of buildings: three alternatives, two scenarios. A case study”, The International Journal of Life Cycle Assessment, Volume 18, March, p. 1082–1088. Menard, Y. et al. (2013) “Innovative process routes for a high-quality concrete recycling”, Waste Management, Volume 33, pp. 1561-1565. Mizutani, R. & Yoshikai, S. (2011) “A New Demolition Method for Tall Buildings: Kajima Cut&Take Down Method”. CTBUH Journal, Issue 4, pp. 36-41. O’Donnell, J., Keane, M., Morrissey, E. & Bazjanac, V. (2013) “Scenario modeling: A holistic environmental and energy management method for building operation optimization”, Energy and Buildings, Volume 62, July, pp. 146-157. Oka, T., Suzuki, M. & Konnya, T. (1993) “The estimation of energy consumption and amount of pollutants due to the construction of buildings”, Energy and Buildings, volume 19, 1993, pages 303-311 Oldfield, P., Trabucco, D. & Wood, A. (2009) “Five energy generations of tall buildings: an historical analysis of energy consumption in high-rise buildings”, The Journal of Architecture, Volume 14(5), pp. 591-613.


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Conference Papers:

Leung, L. & Weismantle, P. (2008) “Sky-Sourced Sustainability - How Super Tall Buildings Can Benefit From Height”, CTBUH Technical Paper, Conference Proceeding, CTBUH 8th World Congress, Dubai, March 3-5,2008

Ahn, C., Rekapalli, P. V., Martìnez, J. C. & Pena-Mora, F., (2009) “Sustainability analysis of earthmoving operations”. Proceeding of Winter Simulation Conference, Austin, TX, pp. 2605-2611.

Matthews, H. S., Roth, M., Sharrad, A. & Bilec, M. (2005) “Economic and environmental implications of construction energy use and generation under new EPA (environmental protection agency) emission standards”, ASCE, Construction Research Congress 2005: Broadening perspectives, San Diego, Califrnia, United States, April 5-7, 2005, pp. 1-7

Ali, M. & Armstrong, P. (2008) “Overview of Sustainable Design Factors in High-Rise Buildings”, Conference Proceeding CTBUH 8th World Congress, Dubai. March 3-5 2008. Balridge, S. M. (2008) ”Tall Structural Sustainability in an Island Context: the Hawaii Experience” , Conference Proceeding CTBUH 8th World Congress, Dubai. March 3-5 2008. Frechette, R. & Gilchrist, R., (2008) “Towards Zero Energy: A Case Study of the Pearl River Tower Guangzhou, China”. Dubai, CTBUH Technical Paper, Conference Proceeding, CTBUH 8th World Congress, Dubai, March 3-5, 2008 Gangolells M., Casals, M., Gassò, S., Forcada, N., Roca, X. (2007) “A methodology for predicting the magnitude of environmental impacts related to the building construction process”, CIB World Building Congress 2007 Ismail, F., Baharuddin, H. & Marhani, M. A. (2013) “Factors towards Site Management Improvement for Industrialized Building System (IBS) Construction” AcE-Bs 2013 Hanoi (ASEAN Conference on Environment-Behaviour Studies), Hanoi Architectural University, Hanoi, Vietnam, 18-21 March 2013, Procedia - Social and Behavioral Sciences, Volume 85, 20 September 2013, Pages 43–50 Kayashima, M., Shinozaki, Y., Koga, T. & Ichihara, H. (2012) “A New Demolition System for HighRise Buildings”, Asia Ascending CTBUH 9th World Congress 2012 Proceedings, pp. 631-636, Shanghai, CTBUH. Kahn, F. (1969) “Recent structural systems in steel for high-rise buildings”, Proceeding of British Constructional Steelwork Association Conference on Steel in Architecture,. British Constructional Steelwork Association: London. Killa, S. & Smith, R. (2008) “Harnessing Energy in Tall Buildings: Bahrain World Trade Center and Beyond”, CTBUH Technical Paper, Conference Proceeding, CTBUH 8th World Congress, Dubai, March 3-5,2008

Nitivattananon, V. & Borongan, G. (2007) “Construction and Demolition Waste Management: Current Practices in Asia”, In: Proceedings of the International Conference on Sustainable Solid Waste Management, 5-7 September, Chennai, India. pp. 97-104 Ochsendorf, J. (2005) “Sustainable Engineering: The Future of Structural Design”, Conference Proceeding Structures Congress 2005: Metropolis and Beyond, New York, New York, United States, April 20-24, 2005, American Society of Civil Engineering, pp. 1 9 Oldfield, P. (2012) “Embodied Carbon and High-Rise”, CTBUH Technical Paper, Conference Proceeding, CTBUH 9th World Congress, Shanghai 2012. Partridge, L, Gan E. S., Wei L., “Factors Influencing Building Energy in Different Climates” CTBUH Technical Paper, Conference Proceeding, CTBUH 9th World Congress Shanghai, 2012. Quick, H. (2005) “Report on foundation design for high-rise buildings”, CTBUH Technical Paper, Conference Proceeding, CTBUH 8th World Congress, Dubai, March 3-5,2008 Shine, K. P., Derwent, R. G., Wuebbles, D. J. & Morcrette, J. J. (2010) “Radiative Forcing of Climate”, IPCC (Intergovernmental Panel On Climate Change). Si, C., Jiang, W., Cui, Y. & He, J. (2012) “Supertall building Pile-Raft Foundation Design on Soft Soil”, CTBUH Technical Paper, Conference Proceeding, CTBUH 9th World Congress, Shanghai 2012.

Tomasetti, R., Abruzzo , J. & Panariello, G. (2005) “Applying the lesson learned from 9/11 to the Remedial Protective Design of Existing Buildings”, Conference Proceeding Paper, Part of: Structures Congress 2005: Metropolis and Beyond, Section: Forensic Engineering Symposium, pp. 1-4, ASCE, New York. Trabucco, D. (2011) “The LCA of Tall Buildings: a Quick Pre-Design Assessment Tool” (unpublished). Seoul, CTBUH. Trabucco, D. (2012) “Life Cycle Energy Analysis of Tall Buildings: Design Principles”, CTBUH Technical Paper, Conference Proceeding, CTBUH 9th World Congress, Shanghai 2012. Trabucco, D., Wood, A., Tabibzadeh, M. & Vassart, O. (2014) “CTBUH Research Project: A Whole Life Cycle Assessment of the Sustainable Aspects of Structural systems in Tall Buildings - Interim Report”, CTBUH 9th World Congress, Shanghai 2012.

Reports: SEI / AISC Thermal Steel Bridging Task Committee (2012) “Thermal Bridging Solutions: Minimizing Structural Steel’s Impact on Building Envelope Energy Transfer”, Supplement to Modern Steel Construction, March, pp. 1-16. BAUFORUMSTAHL (2008) “Architect’s Guide Facilitating the market development for sections in industrial halls and lowrise buildings (SECHALO”. In: P. T. a. C. Arcelor Mittal, ed. Steel Buildings In Europe. Multi-Story Steel Buildings. s.l.:s.n. BIS (2010) “Estimating the amount of CO2 emissions that the construction industry can influence, Supporting materials for the Low Carbon Construction” IGT Report, Crown: London Bovis Lend Lease (2014) “Noise Mitigation Program”. [Online] Available at: http://www. renewnyc.com/content/pdfs/130libertyNoiseM itigationProgramNotarizedMarch27_2009.pdf Bentz, D., Ferraris, C. & Snyder, K. (2013) “Best Practices Guide for High-Volume Fly Ash Concretes: Assuring Properties and Performance”, NIST (National Institute of Standards and Technology), Department of Commerce, Technical Note 1812.


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CTBUH Organizational Structure & Members

Board of Trustees Chairman: David Malott, Kohn Pedersen Fox, USA Vice-Chairman: Timothy Johnson, NBBJ, USA Executive Director: Antony Wood, CTBUH / Illinois Institute of Technology, USA / Tongji University, China Secretary: Craig Gibbons, Arup, Australia Treasurer: Steve Watts, Alinea Consulting LLP, UK Trustee: Joseph Chou, Taipei Financial Center Corporation, Taiwan Trustee: Mounib Hammoud, Jeddah Economic Company, Saudi Arabia Trustee: Dennis Poon, Thornton Tomasetti, USA Trustee: Kam-Chuen (Vincent) Tse, Parsons Brinckerhoff, Hong Kong China Office Board Murilo Bonilha, United Technologies Research Center, Shanghai Jianping Gu, Shanghai Tower Construction & Development, Shanghai Eric Lee, JLL, Hong Kong David Malott, Kohn Pedersen Fox, New York, USA Wai Ming Tsang, Ping An Real Estate, Shenzhen Antony Wood, CTBUH / Illinois Institute of Technology, USA / Tongji University, China Changfu Wu, Tongji University, Shanghai Junjie Zhang, ECADI, Shanghai Kui Zhuang, CCDI, Shanghai Staff / Contributors Executive Director: Antony Wood Associate Director: Steven Henry Operations Manager: Patti Thurmond China Office Director: Daniel Safarik Research Manager: Dario Trabucco Leader Coordinator / Events Manager: Jessica Rinkel Membership Coordinator: Carissa Devereux Digital Platforms Manager: Son Dang Production Associate: Marty Carver Staff Writer / Media Associate: Jason Gabel Staff Writer / Communications Coordinator: Alannah Sharry Staff Writer / Media Assistant: Benjamin Mandel Website Content Editor: Aric Austermann Production Associate: Kristen Dobbins Events Assistant: Chuck Thiel Research Assistant / China Operations: Peng Du Skyscraper Database Editor: Marshall Gerometta Skyscraper Database Assistant: Will Miranda Publications Associate: Tansri Muliani General Counsel: Matt Rossetti Special Media Correspondent: Chris Bentley Advisory Group Chair: Peter Weismantle, Adrian Smith + Gordon Gill Architecture, USA Ahmad K. Abdelrazaq, Samsung Corporation, Korea Donald Davies, Magnusson Klemencic, USA Johannes de Jong, KONE Industrial Ltd., Finland

Jean-Claude Gerardy, ArcelorMittal, Luxembourg Faudziah Ibrahim, KLCC, Malaysia Abdo Kardous, Hill International, China James Parakh, City of Toronto, Canada Mic Patterson, Enclos, USA Glen Pederick, Waterman International, Australia Robert Pratt, Tishman Speyer Properties, China Mark P. Sarkisian, Skidmore, Owings & Merrill LLP, USA Working Group Co-Chairs BIM: Stuart Bull Demolition: Dario Trabucco Façade Access: Lance McMasters, Kevin Thompson & Peter Weismantle High Performance Façades: Christopher Drew & Mikkel Kragh Legal Aspects of Tall Buildings: Victor Madeira Filho & Arthur Wellington Performance Based Seismic Design: Ron Klemencic & John Viise Security: Sean Ahrens & Caroline Field Sustainable Design: Antony Wood Tall Timber: Carsten Hein & Volker Schmid

Philippines: Felino A. Palafox Jr., Palafox Associates Poland: Ryszard M. Kowalczyk, University of Beira Interior Qatar: Shaukat Ali, KEO International Consultants Romania: Mihail Iancovici, Technical University of Civil Engineering of Bucharest (UTCB) Russia: Elena A. Shuvalova, Lobby Agency Saudi Arabia: Bassam Al-Bassam, Rayadah Investment Company, KSA Singapore: Juneid Qureshi, Meinhardt (S) Pte Ltd. South Korea: Dr. Kwang Ryang Chung, Dongyang Structural Engineers Co., Ltd Spain: Iñigo Ortiz Diez de Tortosa, Ortiz Leon Arquitectos Sri Lanka: Shiromal Fernando, Civil and Structural Engineering Consultants (Pvt.) Ltd Taiwan: Cathy Yang, Shanghai Tower Turkey: Can Karayel, Langan International UAE: Dean McGrail, WSP Middle East United Kingdom: Steve Watts, alinea consulting LLP Vietnam: Phan Quang Minh, National University of Civil Engineering

CTBUH Organizational Members (as of July 2015) http://membership.ctbuh.org

Committee Chairs Urban Habitat / Urban Design: James Parakh, City of Toronto Planning Department, Canada Expert Peer Review Committee: Antony Wood, CTBUH / Illinois Institute of Technology, USA / Tongji University, China Height & Data: Peter Weismantle, Adrian Smith + Gordon Gill Architecture, USA Awards: Mun Summ Wong, WOHA, Singapore Expert Chinese Translation Committee: Nengjun Luo, CITIC HEYE Investment CO., LTD., China Skyscraper Center Editorial Board: Marshall Gerometta, CTBUH, USA Young Professionals: Sasha Zeljic, Gensler, USA Regional Representatives Australia: Bruce Wolfe, Conrad Gargett Architecture Belgium: Georges Binder, Buildings & Data S.A. Brazil: Antonio Macedo, EcoBuilding Consultoria Cambodia: Michel Cassagnes, Archetype Group Canada: Richard Witt, Quadrangle Architects Costa Rica: Ronald Steinvorth, IECA International Denmark: Julian Chen, Henning Larsen Architects Finland: Santeri Suoranta, KONE Industrial, Ltd. France: Trino Beltran, Bouygues Construction Germany: Roland Bechmann, Werner Sobek Stuttgart GmbH & Co. India: Girish Dravid, Sterling Engineering Indonesia: Tiyok Prasetyoadi, PDW Architects Israel: Israel David, David Engineers Italy: Dario Trabucco, Iuav University of Venice Lebanon: Ramy El-Khoury, Rafik El-Khoury & Partners Malaysia: Matthew Gaal, Cox Architecture Mongolia: Tony Mills, Archetype Group Myanmar: Mark Petrovic, Archetype Group

Supporting Contributor AECOM ARCADIS ARK Studio West | Architect Reza Kabul Beijing Fortune Lighting System Engineering Co., Ltd. BuroHappold Engineering CCDI Group CITIC HEYE Investment CO., LTD. Dow Corning Corporation Emaar Properties Hudson Yards Illinois Institute of Technology Jeddah Economic Company Kingdom Real Estate Development Kohn Pedersen Fox Associates KONE Industrial Lotte Engineering & Construction National Engineering Bureau Otis Elevator Company Pace Development Corporation Ping An Financial Centre Construction & Development Renaissance Construction Samsung C&T Corporation Schindler Top Range Division Shanghai Tower Construction & Development Shenzhen Parkland Real Estate Development Co., Ltd. Skidmore, Owings & Merrill Sun Hung Kai Properties Limited Suzhou Zhongnan Center Development Taipei Financial Center Corp. Turner Construction Company Underwriters Laboratories WSP Group Zhongtian Urban Development Group


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Patron Arabtec Construction Blume Foundation BMT Fluid Mechanics Bund Finance Center, The Citic Pacific DeSimone Consulting Engineers Durst Organization, The East China Architectural Design & Research Institute Empire State Realty Trust Gensler Hoboken Brownstone HOK, Inc. Hongkong Land ISA Architecture KLCC Property Holdings Berhad Langan Meinhardt Group International NBBJ Permasteelisa Group Ridley Shenzhen Overseas Chinese Town SL Green Management Studio Libeskind Thornton Tomasetti ThyssenKrupp AG Tishman Speyer United Technologies Corporation Weidlinger Associates Wordsearch Zuhair Fayez Partnership Donor Adrian Smith + Gordon Gill Architecture ALT Limited American Institute of Steel Construction Aon Fire Protection Engineering Arquitectonica International Arup Aurecon BALA Engineers Broad Sustainable Building Co. Brookfield Multiplex CBRE Group CH2M HILL China Architecture Design & Research Group Enclos Corp. Fender Katsalidis Frasers Property Halfen United States Henning Larsen Architects Hill International Hyder Consulting Jensen Hughes JORDAHL Jotun Group, The Laing O’Rourke Larsen & Toubro Leslie E. Robertson Associates Magnusson Klemencic Associates MAKE McNamara / Salvia, Inc. Nishkian Menninger Consulting and Structural Engineers Outokumpu PDW Architects Pei Cobb Freed & Partners Pickard Chilton Architects PNB Merdeka Ventures Sdn. Berhad

PT Gistama Intisemesta Quadrangle Architects Rowan Williams Davies & Irwin SAMOO Architects and Engineers Saudi Binladin Group / ABC Division Schüco Severud Associates Consulting Engineers Shanghai Construction (Group) General SHoP Architects Shum Yip Land Company Limited Sika Services AG Sinar Mas Group - APP China Solomon Cordwell Buenz Studio Gang Architects Syska Hennessy Group TAV Construction Terracon Time Equities Tongji Architectural Design Group Walsh Construction Company Walter P. Moore and Associates WATG Werner Voss + Partner Contributor Aedas AkzoNobel Alimak Hek Alinea Consulting Allford Hall Monaghan Morris Altitude Façade Access Consulting Alvine Engineering AMSYSCO ArcelorMittal architectsAlliance Architectural Design & Research Institute of South China University of Technology Architectural Design & Research Institute of Tsinghua University Architectus Barker Mohandas, LLC Bates Smart Benson Industries Inc. bKL Architecture Bonacci Group Bosa Properties Inc. Boundary Layer Wind Tunnel Laboratory Bouygues Construction British Land Company Broadway Malyan Brunkeberg Systems Cadillac Fairview Canary Wharf Group Canderel Management CB Engineers CCL Cermak Peterka Petersen Chapman Taylor Clark Construction Conrad Gargett Continental Automated Buildings Association Cosentini Associates CS Group Construction Specialties Company CS Structural Engineering CTSR Properties Cubic Architects Dar Al-Handasah (Shair & Partners) Davy Sukamta & Partners Structural Engineers DCA Architects

DCI Engineers Deerns DIALOG Dong Yang Structural Engineers dwp|suters Elenberg Fraser EllisDon Corporation Euclid Chemical Company, The Eversendai Engineering Qatar Façade Tectonics FXFOWLE Architects GERB Vibration Control Systems (USA/Germany) GGLO Global Wind Technology Services Glumac gmp • von Gerkan, Marg and Partners Architects Goettsch Partners Grace Construction Products Gradient Wind Engineering Inc. Graziani + Corazza Architects Guangzhou Design Institute Hariri Pontarini Architects Harman Group, The Hathaway Dinwiddie Heller Manus Architects Hiranandani Group Housing and Development Board Humphrey & Partners Architects, L.P. Hutchinson Builders Irwinconsult Pty. Israeli Association of Construction and Infrastructure Engineers JAHN Jaros, Baum & Bolles JDS Development Group Jiang Architects & Engineers JiangSu Golden Land Real Estate Development Co., Ltd JLL John Portman & Associates Kajima Design KEO International Consultants KHP Konig und Heunisch Planungsgesellschaft Langdon & Seah Singapore LeMessurier Lend Lease Lusail Real Estate Development Company M Moser Associates Maeda Corporation Mori Building Company Nabih Youssef & Associates National Fire Protection Association National Institute of Standards and Technology NIKKEN SEKKEI LTD Norman Disney & Young OMA Omrania & Associates Ornamental Metal Institute of New York Palafox Associates Pappageorge Haymes Partners Pei Partnership Architects Perkins + Will Plus Architecture Pomeroy Studio Project Planning and Management Pty Ltd PT Ciputra Property R.G. Vanderweil Engineers Rafik El-Khoury & Partners Ramboll RAW Design

Supporting Contributors are those who contribute $10,000; Patrons: $6,000; Donors: $3,000; Contributors: $1,500; Participants: $750.

186 | CTBUH Organizational Structure & Members


Read Jones Christoffersen Related Midwest RMC International Ronald Lu & Partners Royal HaskoningDHV Sanni, Ojo & Partners Schöck United States Sematic S.r.l. Shanghai Jiankun Information Technology Co., Ltd. Shimizu Corporation SilverEdge Systems Software Silverstein Properties Soyak Construction and Trading Co. Stanley D. Lindsey & Associates Steel Institute of New York Stein Ltd. SuperTEC (Super-Tall Building Design & Engineering Tech Research Center) Surface Design SWA Group Takenaka Corporation Taylor Devices, Inc. Tekla Corporation Terrell Group TFP Farrells TMG Partners TSNIIEP for Residential and Public Buildings Uniestate University of Illinois at Urbana–Champaign UrbanToronto Vetrocare Waterman AHW (Vic) Pty Ltd. Weischede, Herrmann und Partners Werner Sobek Group Wilkinson Eyre Architects WOHA Architects Woods Bagot WTM Engineers International WZMH Architects Y. A. Yashar Architects YKK AP Façade Participants There are an additional 255 members of the Council at the Participant level. Please see online for the full member list. http://members.ctbuh.org


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We now find ourselves in an age where “green design” is at the forefront of many tall building projects around the world, where it seems that every year brings new technologies and innovations that are touted as the be-all and end-all for a long-term sustainable future. But these solutions tend to only reduce the environmental impacts of a building during its operation phases, with the stages before and after this period often neglected. This is perhaps best illustrated by the fact that the world is currently constructing tall buildings in excess of 1,000 meters in height yet we have never demolished a building of even 200 meters in height through conventional means. Despite this reality, our cities continue to be filled with myriad skyscrapers, most of which are not given full considerations for their entire life cycle, or end-of-life. Through the Life Cycle Assessment (LCA) methodology, we can gauge the environmental consequences of human actions by analyzing the flow of materials used in a building and trace the environmental impacts linked to each stage of its life cycle. When information from each stage is combined, a holistic picture of environmental impacts can be formed for a given product, one that acknowledges the various actions that are required to bring a single entity into existence through contemporary means. This research identifies and compares the life cycle implications for the structural systems found in 60- and 120-story buildings. It is intended to inform the international community of professionals and researchers specializing in tall buildings on the life cycle environmental performance of the most common structural systems by providing the most accurate, up-to-date analysis on two key impact categories: Global Warming Potential (GWP) and Embodied Energy (EE). In doing this it presents interesting research results, and also lays down a methodology in this emerging field for others to follow.

Research Funded by:
