AEC Tech News: 2D to 3D #13

25 May, 2005 By: Arnie Williams

Cadalyst AEC Tech News3D Bubbles to the Surface

For an Olympics swim center design based on the physics of water and soap, only three dimensions would suffice

When planners were conceptualizing the swim center for the 2008 Olympics in Beijing, China, there was no way 2D could be the design method of choice. The entire design evolved around organic complexity, with the molecular structure of water and naturally forming soap bubbles as a guiding vision.

An international design competition was held in 2003 for the giant swim center, which would have six pools and a budget exceeding $100 million. A consortium made up of technical services provider Arup, architectural firm PTW and CSCEC (China State Construction and Engineering Competition) won the contract with a proposal to base the design of all pools and the pool area on the natural design of soap bubbles. The concept was to give the pools and surrounding areas an organic appearance based on research into the physics of water and soap bubble formation.

The consortium won the contract and has been busy at work ever since. Scheduled to wrap up next year, two years in advance of the Olympics, the design and construction work has from the outset centered on 3D and Bentley Systems technology.

Putting 3D to the Test
In the early stages of design, which actually took place as part of the competition to win the contract, Arup designers used Bentley MicroStation TriForma to generate a 3D array of a soap bubble cell. They rotated it about two axes, then sculpted a building. The building structure, in 3D, was a Virendeel space frame about 175 meters on each side and 35 meters high — all based on a geometric cell made up of 12 pentagons and two hexagons, which is repeatable in 3D without leaving any empty spaces. Covering this frame would be translucent bubbles. (Click here to view a rendering.)

Don't even try to imagine creating such a structure in 2D — the consortium didn't. The modeling and documentation of the process was a "daunting proposal," says Stuart Bull, a senior 3D technician at Arup. After designers created a 3D centerline wire frame, he notes, they imported the structure into a structural analysis program and then output it as a text file that contained the geometric and structural member design data. Next, Arup team members wrote MicroStation VBA routines that drew upon this data to create a complete 3D model of the structure — a mix of surfaces, solids and structural elements.

The ability to incorporate VBA programming into the design work for such a complex molecular structure was crucial for working with the 3D CAD model, notes Bull. The structure had more than 22,000 beams and 12,000 nodes — the VBA automation, he says, saved Arup months of manual 3D modeling.

Jack of All Trades
But the winning bid wasn't based on the computer model alone. The consortium also had to present a physical model of the structure to an international panel of judges, all of whom were architects. The designers were able to create the physical model by exporting a copy of the 3D model as an STL (stereolithography) file that was used to create a rapid prototype of the model.

But as with most architectural design projects, 2D construction drawings are still a part of the mix, and Bull notes that MicroStation delivered. "Bentley Structural's capabilities, such as automatic drawing extraction, dramatically reduced the time needed to produce 2D documentation," he says. "Since we didn't have to worry about that part of our workload, we could focus on the 3D model."

It will be several more years before the eyes of the world focus on Beijing's National Swim Center, but when they do, they'll be getting an almost microscopic glimpse into a 3D organic design that no other swim center can equal.

Bentley Systems MicroStation