Digging into 3D Modeling Unearths Many Worms
Attention building-information-modeling rookies: Experiences of BIM veterans in the following pages of ENR may save you from reinventing many spokes on the still-rickety wheels of the wagon rolling toward glitch-free use of high-tech tools to make building design and construction less bumpy. The first piece of advice to first-time travelers down the BIM road is to get BIM’s equivalent of driving lessons and roadside assistance. Warning: If you go it alone, you may get into serious trouble. Even modeling veterans can benefit from a BIM “global positioning system.” The helpers call themselves BIM managers or model integrators. The name doesn’t matter. Find someone who has already been through the steep learning curve, and snag that person as a guide.
To help its design team for a federal courthouse project in Jackson, Miss., create BIMs to produce coordinated 2D drawings, the U.S. General Services Administration hired Ghafari Associates, Dearborn, Mich. One of the consultant’s first tasks was to help select the tools best suited to the project. “We were clueless,” says Brian Kimsey, professional services division director in GSA’s Southeast Sunbelt Region, Atlanta. “We learned a lot, initially about the differences and similarities of all the BIM tools,” he says. “We even had Ghafari model a portion of the building as a test, using three different platforms, in the project architect’s office.
GSA eventually selected its platform based on the tool that was best suited to GSA’s primary goal of using BIM for design document coordination (see p. 30).
BIM means different things to different team members, even among the various design disciplines. No one disputes BIM’s potential, especially to find building component conflicts such as a pipe crashing through a beam. In the courthouse project, which is a BIM pilot project for GSA, a comparison was made of two drawing reviews for constructibility issues and system conflicts. One was done on the coordinated model by the project team and the other was done on the 2D drawings produced from the model by an independent review team. The model reviewers found 257 constructibility issues and 7,213 conflicts. The conventional reviewers found six constructibility issues and one conflict.
On the down side, there also is consensus that no matter whether BIM is for architecture, engineering or construction, the learning curve for first-time users is extremely steep. Even those with experience run into roadblocks and have to spend or waste time finding alternate routes.
BIM veterans also agree that modeling changes the design and construction process. The idea is simple: eliminate redrawing the drawings by putting information in once and using it over and over again; catch conflicts before construction begins rather than in the field, when construction dollars are being spent; and use VDC for estimating, scheduling and fabrication. The execution is difficult. BIM veterans caution rookies to hang on tight and expect the unexpected.
The redesign of the design process needs to take into account the order of construction and model content. It’s important to resist the urge to model until protocols are worked out and the program is set.
Sources have learned the hard way that there are no minor design changes, especially if models have already been coordinated. For example, if an engineer moves a beam it can affect other systems, and their models, down the food chain. Models then have to be reviewed, adjusted, checked and re-coordinated.
In the best of all worlds, the contractor and prime trade contractors should be in the room during design process redesign and at times, during design. Input on cost, constructibility and schedule can save model rework and field problems.
Design-construction collaboration is not as easy in a traditional design-bid-build environment as it is with integrated project delivery, design-build and construction management at-risk. For an IPD hospital project for Sutter Health, 30 leaders of the building team spent nearly six months redesigning the design process, moving sticky notes around on a wall (see p. 28).
BIM means more time is spent on design. This can be irksome to designers if they are not compensated. Many maintain they are doing the contractors’ work, without reward. Designers also find that to produce 2D drawings from BIMs they must revamp traditional in-house workflows to align with 3D model conventions.
At BIM’s conception, many expected there would be one BIM per building. The lesson learned is most BIM-enabled projects have myriad models. Many times the design model cannot be used by the trade contractor directly, thanks to software incompatibility or set-up, or both. Most often designers won’t give their models to the contractor for fear of liability if there is a computer glitch or a dimensional inaccuracy. Those that do share usually issue a disclaimer, “Use this at your own risk, for reference only.” That means the contractor has to check every detail of a design BIM. Often, the trade contractor’s detailer finds it easier to create a model from 2D drawings produced from the design model.
On the courthouse project, there are more than 19 design BIMs and more than 60 construction BIMs. On the hospital, so far there are 125 models. That number is expected to grow to 220.
So much for the idea of one model per project. So much for the idea of entering information once and using it over and over again. So much for reducing the likelihood of human error while remodeling.
Sources advise that if BIM is a mandate from above, be sure to nail down owner’s expectations for each building team member—especially if they are not outlined in a contract. Speak up if the expectations seem unreasonable or unreachable. Owners can be naive about BIM’s capabilities.
BIM vets emphasize how important it is for everyone to define terms on a BIM-enabled project. Many errors are a result of poor communication or the unwillingness to share preliminary information early.
Designers have found that too much detail in a model can be a problem. Contractors are finding the opposite is often true. For a recently completed baseball park in New York City, the construction manager at-risk learned that the more trades that model, the better it is for the job (see p. 32). As a result of the project, the CM has written its own BIM protocols, to make the next job that much easier.
By contrast, a contractor for a hospital in Elgin, Ill., found the more-the-merrier modeling approach might not be appropriate. Unlike a ballpark, medical equipment tends to change at the last minute to accommodate the latest technology. With a hospital, time spent modeling too early may be time wasted.
To model or not is just one of the questions that can only be answered based on the specific project at hand, agree sources. Perhaps the biggest BIM lesson of all, depending on the details, is BIM means many different things to so many people.
