accordingly generate a new conceptual cost estimate. 1. ... building data from CAD is desirable for application of VR within the industry. The reason for this is to.
Congrès annuel de la Société canadienne de génie civil Annual Conference of the Canadian Society for Civil Engineering Montréal, Québec, Canada 5-8 juin 2002 / June 5-8, 2002
VIRTUAL 3D CONCEPTUAL COST ESTIMATING MODEL A. JradeA, S. AlkassB A Department of Building Civil and Environmental Engineering, Concordia University, Canada B Department of Building Civil and Environmental Engineering, Concordia University, Canada
ABSTRACT: This paper proposes a framework to develop and implement a Web based model that automates the preparation of conceptual cost estimates by combining Computer Integrated Construction (CIC) and Virtual Reality (VR) environments. The model will automatically generate conceptual estimates after modifying a 3D CAD drawing through CIC. It provides the user the option to visualize and simulate the drawing and its cost data through VR environment. Having done that, it will allow owners, architects and cost engineers to view a constructed building project, change its geometric objects and shapes, and accordingly generate a new conceptual cost estimate. 1.
INTRODUCTION
Conceptual cost estimates are carried out prior to starting the design process of a project. At this stage, data from similar previously executed projects, if available, own experience and wide imagination administer the preparation of these estimates. This is a time consuming process because normally this data is not available or at most it is incomplete. Furthermore, errors occurrence and inaccurate estimates generation are likely to happen. To overcome these problems, researchers have been working on developing management tools in a form of decision support systems to assist in improving the construction process. This is done through the application of computer-modeling techniques to construction related problems in order to improve quality, increase efficiency and to reduce time and cost. Such management tools would improve the efficiency and accuracy of the entire construction process by integrating different types of information within computer-based environment. This process is valuable during cost estimating that converts design information into construction information, which is a core among the whole information related to construction projects (Kim, Oh, Sung 2000). Construction integration has been addressed through several efforts and developments varying from: integration at the application level (i.e. project repository of information), geometrical integration at level of CAD packages, knowledge-based integration between applications and databases, and object-oriented models integrating product and process information to promote collaboration among AEC (Architecture / Engineering / Construction) agents (Zahnan 2001). The benefits of using computer simulation technologies during the design and development of projects start to be realized in the construction industry. The purpose of simulation is to better understand the prospective creation or changes before the physical implementation through various mechanisms. Virtual Reality (VR) technology provides promising characteristics (Chiu 2000). Virtual Reality Modeling Language (VRML) is an open standard that offers the possibility of accessing many types of construction project information using readily available and well-accepted graphical user interfaces based on 3D visualization of a model rather than paper (Lipman 2000). Many studies have been conducted in recent
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years recommending the use of integration and VR/3D technologies to simulate and model construction processes (Aouad, Sun, Bakis 2000). In the construction industry, geometric building data is stored in CAD systems, such as AutoCAD. While it is possible to develop VR models within VR packages, it is widely agreed that transfer of the geometrical building data from CAD is desirable for application of VR within the industry. The reason for this is to reduce repetition and data redundancy (Whyte, Bouchlaghem, Thorpe 1998). This paper aims at modeling the preparation of conceptual cost estimate within the Virtual Reality (VR) environment in conjunction with Computer Integrated Construction (CIC). The model is designed to benefit from the web technology.
2.
PROPOSED MODEL
The proposed model is a web-based integration of 3D CAD drawings and databases through a combined application of CIC and VR environment. The development can be achieved through two phases. The first phase consists of applying CIC techniques to integrate AutoCAD drawings with an External Relational Databases in an attempt to automate the preparation of conceptual cost estimates. Whereas the second phase deals with creating a dynamic link between CAD and Virtual Reality Modeling Language in order to transfer data from CAD to VR. These two phases are later combined in an integration environment allowing for easy exchange of data and information during the conceptual estimation process. These two phases are explained in more details throughout the following paragraphs:
2.1
Phase One
The implementation of this phase is subdivided into three stages. The first two are carried out independently; thereafter, the third is to integrate them in a combined module. 2.1.1
Stage 1
This stage consists of designing and implementing a number of relational databases that contain cost data of previously executed projects in both metric and imperial units. They are based on both the Masterformat (67 projects) and the Uniformat (35 projects) Work Breakdown Structure (WBS) to be used for generating parametric estimates. Furthermore, another database that include published cost data (R.S. Means) based on the Masterformat WBS in both units is designed and implemented for preliminary estimates. The methodology followed in designing this stage was based on providing the user with reliable data where needed to include the following features (Jrade, Alkass 2001): 1. For parametric estimates, employ previously executed projects cost data as historical data (100 projects in both WBS). 2. Adjust this historical data according to city indices, inflation, size, height and perimeter if needed. 3. Provide built-in cost data for preliminary estimates based on published cost data (R.S. Means), which can be modified and enhanced according to the user needs. 4. Generate graphical, tabulated, and organized take off list output reports. The architecture of this stage is shown in Figure 1. The process starts with the user selection of the estimate type. In case of preliminary estimate, the user enters project information, selects the cost data type, unit, city and items quantity. Thereafter output reports are produced as cost summary either tabulated or graphical, as well as a take off items list. It is to be noted that this type of estimates presently is not associated with CAD drawings.
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IN P U T R E Q U IR E M E N T S P a r a m e tric M o d u le s
S T A G E 1 A R C H IT E C T U R E D a t a A n a ly s is
W B S - M a s t e rfo r m a t - U n ifo rm a t
S ta g e 1 D a ta b a s e s
M e tric
Im p e ria l
P a r a m e tric
WBS C ity
A d ju s tm e n t -L o c a tio n -In fla t io n -S iz e -H e ig h t -P e rim e ter
P re lim in a r y M o d u le - P ro je c t In fo rm a tio n - C o s t D at a - P u b lis h e d - Ow n - U n it - Im p eria l - M e tric - C ity - Ite m s Q u a n tit y
P re lim in a r y P u b lis h e d C ost
A d ju s t m e n t -C ity In d e x -In fla t io n R a t e -S iz e -H e ig h t -P e rim e te r
O w n C ost
- Ite m D ir e c t - P ro je c t In d ire c t
C R IT E R IA
•D ire c t C o s t - M a te ria l - L ab or •In d ir e c t C o s t
D a ta S o u r c e - P u b lis h e d - Own
T o t a l C o s t C a lc u la tio n s - E a c h D iv is io n - P e r U n it A r e a - W h o le P ro je c t
U n it - Im p e ria l - M e tric
OUTPUT P ro je c t C o s t E s tim a t e s - P ar a m etric - P re lim in a ry
C o s t S u m m a r y R e p o rt C h a rt T a b u la te d D e t a il - P ie - C o lu m n
Ite m s T a k e o ff L is t
Figure 1 - Stage 1 Architecture For parametric estimate selecting unit, WBS, and city allows the user to adjust data for selected project for inflation, size, height and perimeter whenever required. Each previously executed project included in the database is to be associated with a 3D CAD drawing showing its external envelops, which consists the second stage of design. Figure 2 shows the components that are included in stage 1.
S T AG E 1 C O M P O N E N TS E S T IM AT E T Y P E
P R E L IM IN A R Y
M ASTERFO RM AT
P U B L IS H E D C O S T D AT A IM P E R IA L
OWN C O S T D AT A IM P E R IA L
P U B LIS H E D C O S T D AT A M E TR IC
P A R A M E T R IC
U N IF O R M A T
OWN C O S T D AT A M E TR IC
P U B LIS H E D C O S T D AT A IM P E R IA L
M ASTERFO RM AT
OW N C O S T D AT A M E TR IC
Figure 2 - Stage 1 Components
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P U B L IS H E D C O S T D AT A IM P E R IA L
OW N C O S T D AT A M E T R IC
2.1.2
Stage 2
This stage involves the design and development of a hierarchy database for all components that are used to create the external envelops of one story for any building project in a 3D mode. The implementation starts first by creating the foregoing components in AutoCAD as blocks. Each block contains its accessories (i.e. windows, doors, ect.) and shows all dimension parameters. A pull down customized menu is to be built-in in AutoCAD so that the blocks are easily accessed. These will be stored in files within AutoCAD so they can be accessed by the user when needed to modify and edit any chosen project. This process will be automated by incorporating a module, created using Auto Lisp and AutoCAD’s Visual Basic for Application, to execute the modification done to the drawing according to the user input. Figure 3 illustrates stage 2-hierarchy structure database.
S T AG E 2 H IERARCHY S T RUCT URE D AT ABASE B UIL DING PR O JEC T
AUT OC AD DR AW ING
3m
3m
BLOCK 1
BLOCK 2
… ..
BLOC K N
65 m
60 m
O ONE NE ST STOR ORY Y EXT EXTER ER N NAL AL C OM PO NE NT S C OM PO NE NT S Figure 3 - Stage 2 Database 2.1.3
Stage 3
After implementing the first two stages, the Computer Integrated Construction (CIC) technique is applied in order to link the two previously mentioned stages. A module is developed using AutoCAD’s Visual Basic for Application (VBA). Once the user makes changes to a drawing, the module reads the new areas of all floors that exist in that drawing workspace. By default, AutoCAD assigns for each area a unique number, which is used by the module to read the areas one at a time and write them to an external database. Subsequently the total area is calculated and accordingly a new parametric estimate is generated based on the modified drawing. Figure 4 shows stage 3 integrated components.
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STAGE 3 INTEGRATED COMPONENTS
AUTOCAD DRAWING
READ
AUTOCAD VBA MODULE
WRITE
EXTERNAL DATABASE LINK
NEW PARAMETRIC ESTIMATE
GENERATE
COST ESTIMATING DATABASES
Figure 4 - Stage - 3 Integrated Components
2.2
Phase Two
This phase starts once phase one is completed and all the involved applications are integrated. This phase comprises the animation of the modified 3D CAD drawing using Virtual Reality (VR) environment. The process of translation from CAD into VR is normally a one-way direction. A CAD model is translated into VR, either directly, or through the intermediate stage of a rendering package (Whyte, Bouchlaghem, Thorpe 1998). Virtual Reality Modeling Language (VRML 2.0) has hierarchy format structure starting by identifying group shape, appearance, material and its children then assigning the transformation coordinates of all the objects involved in the scene. Figure 5 shows a sample example of the VRML coding. Thus the whole 3D model can be simulated after writing long programming lines using VRML 2.0, but that is not the research objective. At present the 3D CAD model, which has (.dwg) file format, is manually exported to 3D Studio Max 3.0 for rendering and from there will be exported with VR (.wrl) format. Figure 6 illustrates this process. Finally the model can be implemented in the web through a Virtual Reality browser. The outlook is to automate the data transfer from 3D CAD to VR without passing through 3D Studio Max. VRML 2.0 is to be integrated with the Object-Oriented programming language JAVA due to its ability to provide a mechanism for enabling objects and to perform calculations when needed. Implementing phases one and two, the procedure is finalized by grouping them together, using CIC and VR environment in one single model.
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V R M L S AM P L E C O D E # V R M L V 2 .0 u tf8 # P ro d u c e d b y A h m a d J ra d e # D a te : W e d n e s d a y J a n u a ry 3 0 1 9 :4 1 :3 5 2 0 0 2 D E F T R A C E T ra n s fo rm { tr a n s la tio n -2 8 5 -5 0 -1 5 c h ild r e n [ Shape { a p p e a ra n c e A p p e a ra n c e { m a te r ia l M a te r ia l { d iffu s e C o lo r 0 .4 9 8 0 3 9 0 .7 4 9 0 2 1 a m b ie n tIn te n s ity 0 .7 4 9 0 2 s p e c u la rC o lo r 0 .0 2 4 9 0 2 0 .0 3 7 4 5 1 0 .0 5 s h in in e s s 0 .5 2 5 tra n s p a re n c y 0 } } g e o m e tr y D E F T R A C E -F A C E S In d e x e d F a c e S e t { ccw TR UE s o lid F A L S E convex TR U E c o o r d D E F T R A C E -C O O R D C o o r d in a te { p o in t [ 2 4 7 .4 7 8 5 -2 4 0 , 2 4 7 .4 7 8 5 -2 4 6 .7 5 7 , 2 7 0 5 -2 4 2 .2 5 2 , 2 9 4 .7 7 4 5 -2 4 2 .2 5 2 , 3 1 7 .2 9 6 5 -2 3 3 .2 4 3 , 2 9 4 .7 7 4 5 -2 2 8 .7 3 9 , 3 0 6 .0 3 5 5 -2 2 8 .7 3 9 , 2 9 4 .7 7 4 5 -2 2 4 .2 3 5 , 2 5 8 .7 3 9 5 -2 4 2 .2 5 2 , 2 4 7 .4 7 8 5 -2 3 3 .2 4 3 , 2 5 8 .7 3 9 5 -2 2 8 .7 3 9 , 2 4 5 .2 2 6 5 -2 4 0 ,
Figure 5 - VRML Sample Code
P H AS E 2 E X P R O TIN G P R O C E S S
EXPORT
DDRRAW AWIN INGG RREENNDDEERRIN INGG PPRROOCCEESSSS
EXPORT
VRML
Figure 6 - Phase 2 Exporting Process
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3.
CONCLUSIONS
The methodology followed to develop a Virtual 3D Conceptual Cost Estimating Model, that provides owners, architects, and cost engineers with a tool to perform conceptual cost estimate, animate, model and modify its associated drawings was described. The model incorporates the process of generating preliminary and parametric cost estimates of building project simultaneously with visualizing its initial drawing virtually on the web. The development procedures are and will be carried out using computer applications used in the industry. For instance, AutoCAD due to its wide use in the engineering field, Microsoft Access 2000 and Visual basic due to their availability and compatibility with AutoCAD, 3D Studio Max, VRML and JAVA scripts. Using the model will result in producing quick and cost effective estimates. Moreover, the perspective of the model is to be simple, user-friendly, flexible, and allows users modifications whenever necessary.
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REFERENCES Aouad, G., Sun, M., Bakis, N., Birchall, S., and Swan, W. (2000) An Integrated Web-Based Virtual Model to Support Housing Proejcts. Proceeding of the 28th IAHS world Congress on Housing, Challenges for the 21rst Century, Abu Dhabi, 433-444 Chiu, M.L. (2000) A Virtual Reality Environment for Construction Simulation. Proceedings of the 17th IAARC/CIB/IEEE/IFAR/IFR International, Taiwan, 1147-1152 Diez, R., Abderrahim, M., Padron, V.M., Celorrio, L., Pastor, J.M., and Balaguer, C. (2000) AUTMOD3: An Automatic 3D Modularization System. Proceedings of the 17th AARC/CIB/IEEE/IFAR/ IFR International, Taiwan, 1033-1038 Jrade, A. and Alkass, S. (2001) Computerized Conceptual Cost Estimating System for Building Projects in Canada. Proceeding of the 29th CSCE Annual Conference, Victoria, B.C., C.26.1 – C.26.7 Kim, Y.S., Oh, S.W., Kim, J.R., Sung, B.J. (2000) The Development of an Automated Cost Estimating System Using 3D CAD and Relational Database Proceedings of the 17th IAARC/CIB/IEEE/ FAR/IFR International Taiwan, 827-833 Lipman, R., Reed, K. (2000) Using VRML in Construction Industry Applications. Web3D – VRML 2000 Symposium Monterey, CA Whyte, J., Bouchlaghem, D., Thorpe, T., (1998) The Promise and Problems of Implementing Virtual Reality in Construction Practice. CIB Zahnan, L. (2001) CAD-Based Project Management Model. M.A.Sc. Thesis, Department of Building, Civil and Environmental Engineering, Concordia University.
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