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Despite liability issues, A/E/C teams are benefiting from sharing their 3D models

By Michael Bordenaro

Risks and rewards

While it is possible to share computer models among professions, subcontractors, and trades, standard practices governing contracts and liability all but demand that architects require their structural engineers, detailers, and fabricators to create their own 2D drawings and 3D computer models. The cost of this redundancy may eventually make it possible to share computer models, suggests Robert Park, Columbia’s chairman and C.E.O. “In a typical three- or four-story, 20,000-square-foot building requiring 1,000 tons of structural steel, the detailing would traditionally cost about $140 dollars per ton,” says Park, who has fabricated steel for Gehry projects and for other architects designing complex steel structures that benefit from computer modeling. “If we received a usable computer model that could go right into an automated detailing program, the cost would come down to $60 per ton.”

 

Rose-Hulman’s White Chapel by VOA has a complex structural-steel system modeled in 3D by fabricator A. Zahner to ensure proper understanding of the member alignment, cladding placement, and other systems interactions. Photo: Courtesy VOA Associates

Although $80,000 is sometimes not a significant amount on a project, there are other savings. “If you then provide the fabricator with a model that can be easily translated to run the CNC equipment, the traditional 10 man-hours per ton for fabrication can be reduced by about 3 man-hours,” says Park. Theoretically, this could bring project savings between $100,000 and $150,000, depending on regional labor costs. Park adds that efficient sharing of a computer building model would accelerate the steel fabrication of this theoretical project by three weeks.

Sharing should not be a liability

Because the legal component of the building process is greatly affected when team members share drawings, it takes the influence of a major architect, such as Frank Gehry, to help change the industry practice. Gehry Technologies’ Dennis Shelden says, “Architects are now capable of doing what is traditionally part of the construction team’s responsibility, and the risks and rewards are substantial.” He notes that in conventional design processes, incongruities between structure and other systems may be papered over until the project moves out of the design team’s scope.

“Sharing digital information provides the possibility to change that, even though the process may fly in the face of what lawyers will tell you,” Shelden says. “The upside is that there are significantly fewer errors and omissions if the 3D computer modeling process is fully coordinated.”

While Gehry is the leading architectural adapter of 3D computer modeling of structural steel, the projects shown here illustrate the growing awareness about the benefits of these processes and the increasing eagerness of architects to incorporate them into their practices.

 

The structural core of the 90-foot glass atrium at the headquarters for California Public Employees Retirement System (CalPERS) supports a glass curtain-wall canopy. Columbia Wire & Iron Works created a structural-steel computer model (right). The computer model confirmed that the design was feasible, had appropriate connections, and was actually able to be fabricated. Without a computer model, the structure would have been too complicated to build. Renderings: Courtesy Angle Detailing