... office of multidisciplinary engineer Arup USA Inc. “This performance limitation precludes simultaneous editing over wide-area networks,” he adds.

Some programs produce poor graphics when cutting sections from the models. That means having to retrace, which breaks the connection between the section and the model, says Brodkin. Other programs limit clear representation of small objects, such as piping and conduit.

Designers worry about legal and insurance ramifications of imperfect software and more (see "Related Links"). “I think there will be lawsuits where something is modeled incorrectly,” says structural engineer Jay Love, a principal with Degenkolb Engineers, Oakland, Calif.

Hardware also is not optimal. “The ideal workstation costs roughly twice that of a CAD workstation,” says Brodkin.

SmithGroup has started migrating to 64-bit MS Windows operating systems for workstations to avoid “out of memory” errors on complex projects. To address WAN limitations, Arup has invested in high-bandwidth connections and network accelerators between each of its offices.

One big roadblock to BIM-enabled design is outside of the building team. Permitting agencies are generally not ready to accept electronic models, though they are becoming aware of the need. “We have to go to a 2D CAD process for documentation, which introduces the possibility of discrepancies,” says Love.

Among the three main design consultancies, mechanical-electrical-plumbing engineers (MEPE) are considered the farthest behind in transitioning to BIM. “They were slow to adopt BIM, did not see a business advantage and have lost a fair amount of market share to trade subcontractors,” says Spata.

MEPEs agree that their biggest BIM software challenge by far is functionality. There is a limited ability to dynamically interface with energy-modeling programs and system design programs, including duct and pipe sizing, according to Gordon Holness, 2008-2009 president-elect of the American Society of Heating, Refrigerating and Air-Conditioning Engineers Inc., Atlanta, and chairman emeritus of architect-engineer Albert Kahn Associates Inc., Detroit.

In May 2007, ASHRAE formed a BIM and interoperability steering committee to aid members. The group hopes to have the first draft of a BIM guide ready for ASHRAE’s Jan. 21 meeting in Chicago and establish basic HVAC terminology, data dictionaries and rule sets.

“Jump into BIM with both feet. Halfway measures do not work best.”

— SCOTT SIMPSON, ARCHITECT

Structural engineers may have a leg up on MEPEs, but they report the same BIM aches as their client-architects. Structural engineers often have to support their client’s BIM platform, even if it differs from their own.

Structural engineers have issues with data accuracy, ownership and sharing data down the construction supply chain. Every time a BIM vendor has a new release, the structural engineer must update all links to its various analysis tools. If release dates for new versions of BIM are not coordinated, “we could be out of commission for a week or two,” says Will Ikerd, director of integrated project delivery for Dallas-based Raymond L. Goodson Jr. Inc.

Larger firms can afford to create their own links to analysis programs; Others can’t. “This is why SEs got away from using the analysis links of BIM,” says Ikerd, who expects the links to improve.

In BIM, correct dimensions rule. In the past, if a structural engineer was within 6 in. of the exact member length, it was fine, says Sean B. Smith, division vice president of A-E Gresham Smith and Partners, Nashville. “If models are going to be used downstream [for computer numerically controlled fabrication], they must be accurate to within 1⁄16 in.,” he says.

BIM software for mechanical systems has “limited” functionality.

— GORDON HOLNESS, MECHANICAL ENGINEER

Size matters in structural engineers’ transition to BIM, says Ikerd. Megafirms have resources and small firms are nimble. The 15- to 30-person firm has the worst of both worlds: corporate bureaucracy and limited resources. Ikerd is cochair of the Structural Engineering Institute-Council of American Structural Engineers BIM committee, formed in 2007. It recently released results of a BIM survey answered by 700 firms (see "Related Links").

BIM is altering the designers’ relationship with builders. Because of BIM, HOK on one project could show that bidders overestimated the extent of precast concrete by 30%, says Spata. Bids came down to meet the budget.

Architects say they are not paid extra for BIM, just as they don’t get paid for any tool. However, some expect to be paid separately if the client wants the model detailed beyond what is needed for construction documents.

“Mid-sized structural engineers are in the �worst� position to make the transition to BIM.”

— WILL IKERD, STRUCTURAL ENGINEER

For most designers, the 2D drawings are still the deliverable. “But it won’t be long until contract documents are BIMs,” says Eric Bogenschutz, an assistant director with BSA LifeStructures, Indianapolis.

Even with growing pains, architects are excited about BIM-enabled design. “We feel we are delivering a more highly coordinated design than we ever have,” says architect Richard L. Nitzsche, principal of Perkins+Will, Chicago. BIM tools can help “transform the role and stature” of the architect, adds Carl Galioto, a partner in the New York City office of Skidmore, Owings & Merrill.