Simulate before Constructing25 Apr, 2007 By: Kenneth Wong
A general contractor's lessons show the value of putting BIM into practice.
Fifteen thousand. That’s the number of construction corrections Barton Malow had to make in a recent project, a 1.3 million-square-foot auto production facility in Mexico. In a job of this magnitude, building systems invariably collide: pipes clash with trusses; beams and walls intersect; and columns sit where the crew needs to be. The project managers had two choices: They could tackle these issues in the field by relocating mortar and steel, or they could deal with them virtually by pushing pixels. The company chose the latter. It’s easier, smarter and (to the delight of the client) much cheaper.Debugging the Building
Founded in 1924, the general contractor and construction management firm Barton Malow is practically an octogenarian, a Michigan institution unto itself. With Daimler Chrysler and General Motors for clients, the company is at the top of the food chain. It’s also a BIM (building information model) practitioner. Two of its staffers literally helped write the book on BIM, called The Contractors’ Guide to BIM. (For more, read “How Many Contractors Does It Take to Scale a Wall?”Cadalyst Daily, December 11, 2006.) The company has been putting the principles outlined in the book into practice in a series of pilot projects. The Mexico site was one of those.
Barton Malow uses digital simulation of the construction process in a conference room before going to the field. In one project, the company caught and eliminated approximately 15,000 construction issues in advance.
When it was time to fit the structural steel frame into the building, about 30 people -- architects, engineers, subcontractors and the owner’s representatives -- filed into a conference room in the company’s headquarters, about 1,700 miles away from the site in central Mexico. The fitting took place on a screen about 7' X 6'. “The meetings are for coordination/constructability review,” explains Mark Falzarano, the company’s manager of BIM. “The purpose is to eliminate any problems we might encounter in the field beforehand.”
The 15,000 construction issues discovered were addressed before construction even began. “Without this process, we wouldn’t have picked up all of those,” admits Jim Dome, the company’s manager of A/E services.
Issues discovered during the construction review meetings range from simple clashes among HVAC elements and structural frames to those that might create major production delays if corrected in the field.
Falzarano points out that the number, though alarming at first glance, is perfectly understandable. For example, one pipe reaching into the trusses can cause multiple interferences, so simply relocating the pipe to clear the trusses may correct a whole series of problems.
The clash report reveals the problem areas as thumbnails.
If a new edition of The Contractors’ Guide to BIM were published, it may need an additional chapter, devoted entirely to developing training strategies, Dome reflects. “We sent some of our people to training [to become proficient in the 3D CAD applications used in BIM]. They get the whole book dumped on them, but maybe what they need is just the first chapter.”
It’s far better to let the trainees absorb the materials in digestible chunks than to expect them to master the entire curriculum, Dome observes. And the hands-on approach that ties the lessons to real-world modeling tasks is more effective than the strictly theoretical learning.
“We now have trainers come in at an appropriate time, and let them coach the people while they’re actually working on a project,” Dome says. Barton Malow primarily uses a mixture of two CAD systems: Bentley’s MicroStation and Autodesk Revit.The Coordination Dance
Both Falzarano and Dome are actively evangelizing the benefits of BIM, especially to the general contractors. People unaccustomed to the BIM workflow and principles may start off with a partial deployment, suggest the authors of The Contractors’ Guide to BIM. One such scenario is “coordinating construction sequencing,” something that’s easier said than done when several teams using different CAD packages are involved.
“Theoretically, with BIM, you’re trying to do everything only once,” Dome explains. “If you know somebody else is creating something -- for instance, the steel structure model you need to hang inside your architectural model -- you don’t want to duplicate the effort unnecessarily. So you wait for it.” And that habit may foster certain interdependencies that hinder work.
“You have to learn to recognize when not to wait any longer,” Dome advises. “You may have to model a particular portion of that expected work to keep the project moving forward, then swap what you’ve created with the model the structural engineer provides when it’s ready.”The Ownership Question
The book also cautions, “The emergence of BIM as a vehicle for dramatic change in design and construction occurs in a legal environment that has not fully come to grips with all the risk management implications of the underlying technology of electronic representation or transmission of documents of any type.”
Because the technology now allows the construction teams to foresee certain problems in advance through digital prototyping, they may now be accountable for much more, Dome points out. “We can now visualize things that we weren’t able to before,” he reasons. “We get multiple chances to [digitally] build and rebuild the building we’ve been asked to create before we construct it in the field."
Because accountability is a legal burden for contractors, it may unnerve some people. The issue is further complicated by the communal environment, where many collaborators are entrusted with the authority to edit and modify the shared 3D model. So what are the liabilities associated with participating and collaborating in the model? The guidebook admits it doesn’t have a finite answer, at least not at the present. Falzarano and Dome recommends distributed responsibilities that correspond to the roles of the collaborators.
“Each discipline or subcontractor should be responsible for the portion of the model they’re required to produce -- till the project is complete. In the end, the integrated 3D model will be handed over to the owner,” says Falzarano.
“It’s the same as in the past, when we took the civil documents, architectural documents, structural documents, and bound them into a construction package. Everybody was responsible for the part that they’d created,” Dome contrasts.
The Contractors’ Guide to BIM points out, “While the risks presented by BIM may be different in some respects, it does not automatically follow that a contractor’s risk should be greater.”