Building Tomorrow’s Society Bâtir la Société de Demain
Fredericton, Canada June 13 – June 16, 2018/ Juin 13 – Juin 16, 2018
UBC BROCK COMMONS ALTERNATIVE STRUCTURAL DESIGN WITH MASS-TIMBER CORES Connolly, Thomas1 Loss, Cristiano1 Iqbal, Asif1,2 and Tannert, Thomas1 1 2
University of Northern British Columbia, Canada
[email protected]
Abstract: The UBC Brock Commons in Vancouver, with its 18 stories and 53 meters height from the ground, was the tallest wood-based hybrid building in the world at the time of completion in 2016. The building has 17 stories of mass-timber superstructure resting on a concrete podium with two concrete cores that act as seismic and wind lateral force-resisting systems. Construction of the mass-timber superstructure took only ten weeks whereas the concrete cores were built in fourteen weeks. There could have been a substantial reduction in the project timeline leading to cost savings, as well as a further reduction of environmental footprint, if mass-timber had been used for the cores. The objective of the research presented in this paper was to evaluate numerically the feasibility to design the UBC Brock Commons using mass-timber cores made of Laminated-Veneer Lumber or Cross-Laminated Timber. The results indicated that applying a series of structural adjustments, i.e. configuration and thicknesses, masstimber cores could meet the seismic and wind performance criteria as per the current National Building Code of Canada. 1
Introduction
With increasing awareness of climate change and its potential consequences there has been a renewed interest in recent years to use sustainable materials for all types of purposes. As a consequence, wood has attracted renewed interests from professionals, developers and the public in general to be used in the building sector. In parallel, there has been considerable progress both in product development and improvement of properties of engineered wood products enabling to construct tall buildings with wood as the primary material. One such building is investigated here to propose further application of wood to promote that as a practical alternative for similar structures in the future. 2
Building Description
The UBC Brock Commons Student Residence (Figure 1) herein also referred to as the UBC Tall Wood Building (TWB) was one of the winners of the ‘Tall Wood Building Demonstration initiative’, launched in 2013 by Natural Resource with the requirement to use mass-timber products in structures of at least ten storeys tall. The 18-storey building has a total building height of 58.5m at the top of elevator parapet, with a typical storey height of 2.8m, a gross floor area of 840m2 (15m x 56m, Figure 1c) and provides 404 beds distributed in single-bed studio or four-bed units located on floors 2 to 18.
Conelly, T., C. Loss, A. Iqbal, and T. Tannert (2018). “UBC Brock Commons alternative structural design with mass-timber cores.” Proceedings of the 6th CSCE International Structural Specialty Conference, Fredericton, Canada, June 13th-16th
Conelly, T., C. Loss, A. Iqbal, and T. Tannert (2018). “UBC Brock Commons alternative structural design with mass-timber cores.” Proceedings of the 6th CSCE International Structural Specialty Conference, Fredericton, Canada, June 13th-16th
Conelly, T., C. Loss, A. Iqbal, and T. Tannert (2018). “UBC Brock Commons alternative structural design with mass-timber cores.” Proceedings of the 6th CSCE International Structural Specialty Conference, Fredericton, Canada, June 13th-16th
Conelly, T., C. Loss, A. Iqbal, and T. Tannert (2018). “UBC Brock Commons alternative structural design with mass-timber cores.” Proceedings of the 6th CSCE International Structural Specialty Conference, Fredericton, Canada, June 13th-16th
Figure 8: Comparison of seismic drifts in the critical direction
Figure 9: Comparison of seismic drifts in the critical direction 4
Conclusions
Based on the numerical investigation presented herein, the use of CLT cores for the UBC TWB does not appear feasible as the full-stiffness CLT model does not meet all lateral drift requirements. Very thick panels would have to be used to satisfy the drift limits, which may not be cost efficient. The introduction of additional CLT walls increases the performance, but not enough to meet the requirements. LVL cores, in contrast, appear to be a more suitable option for use in the building. The full-stiffness, 445mm thick LVL core model meets all requirements while providing performance comparable to the concrete cores. The introduction of the “C” shaped walls slightly decreases the maximum drifts. However, these walls introduce more torsion when considering the X-direction earthquake visible by the increase in Y-direction drift. The associated cost of adding these walls would likely be too high to justify the marginal performance increase.
References Acton Ostry Architects, "Projects: Brock Commons Tallwood House," Available online: http://www.actonostry.ca/project/brock-commons-tallwood-house/. Canadian Standards Association, CSA A23.3-14: Design of Concrete Structures, Mississauga: CSA Group, 2014. Canadian Standards Association, CSA086-14: Engineering Design in Wood (Supplement), Missisauga: CSA Group, 2016. Dlubal Software, RFEM Finite Element Software Version 5.11, 2017. National Building Code of Canada, National Research Council, Ottawa, 2015. E. Poirier, M. Moudgil, A. Fallahi, S. Staub-French, T. Tannert “Design and Construction of a 53 Meter Tall Timber Building” World Conference on Timber Engineering, Vienna, Austria 2016a. E. A. Poirier, A. Fallahi, M. Moudgil, T. Tannert and S. Staub-French, "UBC Tall Wood Building Case Study (Design and Pre-Construction Phase)," Forestry Innovation Investment BC Wood First Program, Vancouver, 2016b. T. Tannert, M. Moudgil , “Structural Design, Approval, and Monitoring of a UBC Tall Wood Building”, ASCE Structures Congress, Denver, 2017.
