Maestros of Design and Construction Render a Virtual Masterpiece

construction.com May 2, 2001

By Harry Goldstein

With their radical, flowing curves and gleaming metallic facades, Frank O. Gehry's organic designs demand a lot from engineers and contractors. The 2,273-seat, $175-million Walt Disney Concert Hall, the new home for the Los Angeles Philharmonic Orchestra, is no exception. The project, scheduled for completion in early 2003, fits one of Gehry's most dramatic designs into a tight one-city-block site at the northern end of downtown Los Angeles.

The physical model of Frank Gehry's Walt Disney Concert Hall. Photo courtesy of Frank O. Gehry & Associates.

On projects this complex, effective communication among stakeholders keys successful execution. In order to facilitate schedule creation and analysis and build a team atmosphere, the project team invited researchers from Stanford University's Center for Integrated Facility Engineering (CIFE), led by graduate student John Haymaker, to build several 4D (3D plus time) models.

Haymaker used prototype 4D modeling software developed as part of an ongoing collaboration between Walt Disney Imagineering Research and Development and Stanford associate professor Martin Fischer's team at CIFE. Last March, Haymaker began to work on site to develop the 4D models. By June, he had finished the first iteration and introduced the general contractor M.A. Mortenson, Minneapolis, Minn., and the subcontractors to the technology, months before the first steel was erected.

A series of 4D models was built for the Walt Disney Concert Hall because the geometry and complexity was too great to handle in one model. Here is a model built for just activities inside the Concert Hall

With that kind of lead-time, the project team was able to visualize several what-if scenarios to ferret out conflicts before the project began. The Imagineering 4D tool's intuitive VRML-based interface made visible scheduling inconsistencies that might otherwise remain hidden in a sea of data until an on-site conflict surfaced.

Communicating schedule details to subcontractors is one of the main benefits of using 4D on the Walt Disney Concert Hall. Greg Knutson, Mortenson's general superintendent on the project, says that the Imagineering tool "has definitely helped " subcontractors to understand their roles as well as aiding Knutson and his schedulers in identifying coordination conflicts.

4D model can also find safety conflicts. This scene shows steel being erected over workers laying metal deck on the Walt Disney Concert Hall

It was important to involve subcontractors early on in the project, says Haymaker. "That was really fun to bring them in and show them the models and have it become a real collaborative process," he recalls. "There's this puzzle on the wall that they can work together to try to solve—we'll work here, you work there. We really saw some teambuilding emerge."

That team later employed the 4D model to resolve scaffolding and hoisting issues. When workers for Permasteelisa USA Inc., Enfield, Conn., started to look at the 4D model, they realized there were a lot of places where they couldn't anchor the mast-climbing HEK lift scaffold, whether because the concrete work would not be finished or because access would be difficult or impossible. Once the 4D model revealed that a HEK lift was not ideal for the project, Permasteelisa decided to employ a swinging scaffold instead.

The 4D models helped discover several coordination conflicts on the Walt Disney Concert Hall project. The metal skin (in blue) needs to rest on top of the concrete (yellow), so that activity should be finished before the metal activity begins

The 4D model also helped subcontractors get a handle on access issues. Since the construction site is right in downtown LA and streets must remain open, lay-down areas were modeled to ensure efficient and unfettered access paths. "Now we've got steel lay down areas, and finish contractors have some lay down areas determined," says Haymaker. "When we plan lay down areas in 4D models, we'll create that geometry and put it into the 4D model and everyone learns what's going on."

Another obvious use for a visualization tool is to inform stakeholders of the approach to construction. For the Disney Concert Hall project, this included communicating the details of the project to the board of directors formed specifically to oversee the project. Since most board members were unfamiliar with the specifics of the construction process, the 4D presentation helped them understand the special challenges of the site and why certain choices were made. Knutson fires up the 4D model for the monthly meeting he has with subcontractors as well as for 90-day look-ahead meetings.

Besides being a planning aide, the 4D tool also serves as an archive of information, and proved especially useful when the first scheduler on the Concert Hall project quit. The new scheduler had to learn what was going on in the first scheduler's mind and 4D helped accelerate that process a great deal, according to Haymaker.

Computer models are only as good as the information that goes into making them, and for the 4D model to continue to be an effective planning tool, Knutson and his schedulers must update the schedules that feed the model on a monthly, if not weekly, basis. But on a hectic job site, other priorities often take precedence. "Sometimes we get so busy, it's hard to fill that extra set of activities," Knutson admits, adding, "We're getting more disciplined there, but sometimes there's a lag."

BUILDING THE CONCERT HALL IN VIRTUAL SPACE
The Walt Disney Concert Hall will have been built once on Grand Avenue and numerous times in virtual space by the time its doors open. The 3D models were constructed by Gehry's team in Dassault Systemes' CATIA CAD/CAM/CAE software package. CATIA uses Non-Uniform Rational B-Splines (NURBs)-based curves and surfaces to render complex geometry. In particular, NURBs provide highly accurate mathematical descriptions of the amorphous organic curves that are the signature of a Gehry design. Gehry's NURBs-powered CATIA model and the open architecture of the Imagineering 4D tool, which was developed to handle any kind of geometry, gave Haymaker the opportunity to create an extremely robust 4D model.

But creating the model wasn't easy. Sometimes Haymaker had to fill in details: Gehry modeled only the surfaces for the metal skin, which requires backing support and clips that were not modeled, but need to be installed. Other times, the 4D modeler had to edit the data down to a manageable level of abstraction. For instance, the steel fabricator submitted a model where all the bolts and holes were depicted, far more information than was needed for the 4D model.

The major challenge was mapping the objects depicted in the 3D model to the 7,200 activities contained in Mortenson's Primavera Project Planner (P3) construction schedule. "The schedule had already been created, the geometry had already been created and the two didn't really sync up," Haymaker explains. "The schedule would create certain activities that would require geometry to come from different files and the way that the architect broke up the geometry was different from how the scheduler broke up the process." This created big problems with nomenclature: Gehry might have named a particular element, "element five," whereas a contractor might have called it the "south wall." These conflicts required Haymaker to reconcile the disparate ways the architect, engineers, and subcontractors broke up the building.

This is the Steel, Concrete, and Exterior Finish model of the Walt Disney Concert Hall. This model depicts steel being erected in two places by two cranes (orange) metal deck being installed (turquoise) and concrete being poured (brown)

"You'd work with the 3D model and the schedule and go back and forth. Divide and conquer," says Haymaker. "There was a lot of sitting down with the scheduler trying to pull down from his brain what he was trying to say." To Haymaker, much of the process of building a 4D model comes down to extracting the picture that the scheduler has in his brain and "trying to draw it out to show to other people….You have to pull it out and define it on the geometry." He points out that the process not only makes the schedule explicit to everyone else, but that it helps the scheduler to be rigorous as to how, for example, he defines the edge of one element in relation to the edge of the element it abuts.

Dennis Shelden, Gehry's director of computing, emphasizes that 4D is "a small part of a much larger approach, a general set of 3D-centric building description tools" used by Gehry. This tool set comprises a portion of what Shelden calls a global approach to 3D modeling that's much closer to how cars and airplanes are designed than how most architectural plans are executed. This also means that Gehry can, and does, provide detailed information for every member of the project team, from the owners down to the fabricators and subcontractors.

The 4D model is an "important visualization and planning tool," and is especially useful to general contractors, says Shelden. Ultimately, however, it's just one high tech tool among many needed to accurately translate Frank Gehry's unique vision from the sketch pad to the site on Grand Avenue between First and Second Streets, where a titanium halo rises to crown the City of Angels.

Glossary

NURBS: Stands for Non-Uniform Ration B-Spline, a way of mathematically representing a 3D object. NURBS can be used to represent so-called analytic shapes such as cones as well as free-form shapes such as the curved surfaces of a Frank O. Gehry design.

VRML: Stands for Virtual Reality Markup Language, which allows 3D objects to be depicted via the Web and also lets the user navigate through a 3D scene, such as a construction site.

Images courtesy of Walt Disney Imagineering/Stanford University

© 2001 The McGraw-Hill Companies - All Rights Reserved