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The architectural interior, structure, and facade of the building are one unified thick/ hollow wall and roof element. The wall cavity is 3.6 meters (11.8 feet) deep, and the cavity that forms the roof is 7.2 meters (23.6 feet) deep.

Most of the solar energy that permeates the building structural zone can be captured to heat the pools and interior areas. For cooling, air is circulated through the cavity by thermal effects.

The entire building contains more than 22,000 steel beam members and 12,000 nodes, with approximately 6,500 tons of steel. This presented a challenge of optimization, as self-weight is critical in long span roof structures.

BIM in Design and Construction

The project was designed in three distinct stages: design competition, design development, and preparation of tender documents. Structural analysis, design, and optimization continued throughout these process stages.

BIM-related issues in this project were conceptual design, structural optimization, rapid prototyping, interoperability, and drawing production. The complexity and originality of the building meant that the design and the models representing it were constantly evolving and changing.

By preparing and applying a variety of sophisticated add-on tools to standard BIM systems, the project team was able to achieve better optimization (structurally and functionally), better analysis schemes, and to meet and sometimes beat short project schedules.

Competition

Geometry was still being defined at the competition stage, so scripts were written in MicroStation VBA that would skin a wireframe to provide a representative 3D solid model. The 3D model created by the scripts consisted of members and node spheres of the same size, while some simple rules defined how to handle members of various lengths.

Full model exports to other modeling packages were only done during the competition stages for the purposes of visualization and rapid prototyping for presentation.

Development

During design development, Arup used Strand 7.0 finite-element analysis (FEA) software for structural analysis. They developed VBA scripts to export the analyzed and optimized MicroStation model to AutoCAD drawing files (DWG format), MicroStation TriForma drawings (DGN), and Excel spreadsheets (XLS) for data extraction.

The analysis data exported to MicroStation included end points and dimensioned section types. Scripts imported data files to recreate wireframe models, with annotations of element number and section type, for integrity checks and production. VBA scripts, called precompiled DLLSD (MicroStation's MDL-based 3D modeling routines), were used to create 3D primitives, constructed in an element-aligned local coordinate system before being translated back into the global coordinate system.

Tender Documentation

True structural elements were established from elements of the 3D wireframe model, aided by a VBA script that applied sectional information, beam reference, and property numbers to the wireframe as invisible attributes for searching.

Each stick element was skinned with a TriForma structural element, giving a fully defined, structurally correct model. Data extraction listed the sections (including nonstandard fabricated rectangular, circular, and square hollow structural sections) in material reports, providing total length, weight, grades, and quantities for each. In this case, 112 sections were needed to document the project.

A completely new 3D model was rebuilt several times from the structural analysis model, using script-based automation. Eventually, extraction of drawings, plans, sections, elevations, and details was all managed by script, with all 65 drawings updated over one weekend. Each section file was created and automatically referenced into a drawing sheet.

Fabrication and Construction

Arup proposed prefabrication to limit onsite welding, but this was rejected by the client in China, who preferred to use a large workforce approach. Approximately 12,000 spherical nodes and 22,000 tube and box sections were individually fixed onsite. There were approximately 3,000 workers onsite, including more than 100 welders.

In a process unique to China, tube and box section preparation was done manually from Arup's cut length spreadsheets. In other countries, Arup's approach would be to provide data in Steel Detailing Neutral Format (SDNF) to enable the use of CNC machinery.

A large number of part drawings were produced in this nonstandard steel job because of the variety of complex connections — exceeding 15,000 drawing views for fabrication on the shop floor. Small items, such as plates and stiffeners, were all attached manually.

Optimization of Structure and Process

To address the structural design, Arup developed a structural optimization program encompassing analysis, design, and design optimization. This included determining member sizes for 22,000 beams to meet the requirements of 13 Chinese steel code strength equations at five points on each beam for 190 load combinations.

Scratch software in Visual Basic ran the optimization process, using a damped constraint satisfaction method, to find three sets of well-graded discrete member cross section choices. Each set was assessed by simulated annealing, plastic-versus-elastic stiffener design, and engineering judgment.

It proved possible to rebuild the 3D fabrication model based on weekly structural analyses and sometimes even daily, updating all related information in a seamless process.

Arup Senior 3D Modeler Stuart Bull explained, "The ability to use MicroStation VBA scripts to create our geometry, which gave us the link from the engineering and analysis model to our working 3D CAD model, was very important."

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This case study was originally prepared by Sherif Morad Abdelmohsen for Professor Chuck Eastman in a course offered in the College of Architecture Ph.D. program at Georgia Institute of Technology, winter 2006. It was adapted for use in the book BIM Handbook by Chuck Eastman, Paul Teicholz, Rafael Sacks, and Kathleen Liston. The authors wish to acknowledge and thank the members of the Arup, PTW, and CSCEC teams, whose contributions were essential to this case study. The insight offered by Stuart Bull of Arup was particularly helpful.

Kathleen Liston, a technology consultant and Ph.D. candidate at Stanford University, cofounded Common Point, a construction simulation software company.

This article is excerpted from BIM Handbook by Chuck Eastman et al., copyright © 2008, with permission of the publisher, John Wiley & Sons.

SUBSCRIPTION SAMPLE The complex glass-and-steel facade of the Water Cube is intended to recall the pattern of bubbles in water. Image: Courtesy Arup, PTW & CSCEC Extra Large Image The irregular steel space-frame structure of the Aquatics Center's walls and roof provide an uninterrupted span over the main pool area. Photo: Courtesy Ben McMillan/ Arup Extra Large Image At the competition stage, data exchanges between MicroStation and Rhino allowed for parallel development of drawings and animations. Image: John Wiley & Sons Axonometric detail drawings of the exterior wall and roof connectors. Image: Courtesy Arup, PTW & CSCEC Extra Large Image Axonometric drawings show the complex wall and roof structural system of the Aquatics Center. Image does not appear in book. Image: Courtesy Arup, PTW & CSCEC Extra Large Image Prefabrication of structural components was rejected by the client in favor of onsite fabrication by over 3,000 workers. Photo: Courtesy Ben McMillan/ Arup Extra Large Image The exterior of the Aquatics Center is covered in 100,000 square meters (1.1 million square feet) of the lightweight copolymer EFTE. Image does not appear in book. Photo: Angus Macleod BIM Handbook: A Guide to Building Information Modeling for Owners, Managers, Designers, Engineers, and Contractors by Chuck Eastman, Paul Teicholz, Rafael Sacks, and Kathleen Liston Image: John Wiley & Sons Extra Large Image   Click on thumbnail images to view full-size pictures.