What's happening in the world of building information modeling (BIM)? A better question may be what's not happening? The construction industry is in a constant state of change and BIM is part of it. There are daily e-mail blasts offering BIM seminars, webinars, and conferences.
As a design and a construction tool, BIM enables both contractors and designers to produce 3-D virtual components that are brought together into a common environment. “The best virtual models result when all parties to a construction are involved in the discussion,” says Dan Russell, simulated construction manager, Sundt Construction, Tempe, Ariz.
What is BIM?
Think of BIM as a virtual building, structure, pavement, or other building project with all the parts and pieces included. “BIM allows you to see a project in 3-D,” says Andy Dickey, manager of the contractor business unit for Tekla North America, Kennesaw, Ga. “It's the way people naturally visualize everything—three-dimensionally. Traditionally, designers develop two-dimensional drawings that can be viewed from different angles, each presenting information about an object in the design. Then people try to visualize what the object looks like and how it fits into the design. BIM removes the guesswork. You can even look inside a rebar cage in location, something you can't do any other way.”
The difference between BIM and a 3-D computer-aided design (CAD) is the inclusion of additional information in the BIM model, allowing you to access product information, retrieve specifications for a part, assemble material orders, complete layout work, construct job completion reports, locate congestion, and more.
Using BIM for design
The design community has embraced the concept of BIM and its collaborative nature, but there is concern that some legal risk could result when contractors use their models for estimating and building if there is inaccurate or incomplete information. Nicholas Holt, a director at Skidmore, Owings, and Merrill (SOM), New York, says his firm currently avoids this issue by providing traditional 2-D plans for bidding purposes. In parallel, SOM provides the BIM model for the project team's use, along with a disclaimer stating that the 2-D documents are the legal contract documents. Legal and insurance industries currently are familiarizing themselves with BIM and collaborative teaming models, as well as any risks. But Holt believes the industry isn't far from the time when 2-D drawings will be a thing of the past. SOM currently uses BIM for about 50% of its projects, while 70% of all their new work incorporates BIM.
Holt says SOM has historically been in the forefront with regard to adopting new technology—the company helped to pioneer digital drawing technology—and it is taking the same approach with BIM and staff training. The company believes BIM provides vital information earlier in the design process, facilitating early decision making and increased productivity.
There are several different BIM software products on the market today, all of which exchange files between each other with varying degrees of success. Holt says they use several products, capitalizing on the strengths of each program. SOM uses Revit by Autodesk, San Rafael, Calif., to assemble all the data and geometry into one model. This model is the platform SOM shares with contractors. Other BIM software used internally includes Rhino from McNeel North America, Seattle, for developing original concept models; Ecotect by Autodesk to analyze sustainability issues; Autodesk's Navisworks to identify clashes between materials; and Tekla Structures from Tekla Inc., Kennesaw, Ga., which specializes in structural concrete and steel design detailing and construction management for all construction organizations. Visit our website for Common BIM Software Serving the Construction Industry and more information about software packages.
As a shared tool, Holt notes when SOM gives its BIM models to contractors, they often use them to add their own data for estimating purposes (5-D), scheduling (4-D), developing shop drawings and coordination drawings, using specific products, or creating as-built drawings—a strong incentive for the construction community to learn how to use BIM.
Tekla and Trimble
Tekla targets the concrete, steel, general contracting, and construction management markets as primary clients. Making constant improvements to its software to increase usability throughout the concrete industry is a top priority. “Two of our strategic audiences are general contractors who self-perform their own concrete work and concrete subcontractors,” says Dickey. “The data that can be embedded in our model allows concrete contractors to estimate, layout materials needed for each construction element, track concrete placing and testing results, and seamlessly move information from BIM to implementation in the field.”
Trimble, Dayton, Ohio, produces a wide range of layout tools for the surveying and construction industries. Of particular interest for BIM purposes are total stations, robotic total stations, 3-D laser scanners, and its handheld computer devices that instruct total stations during layout work; Trimble refers to these as LM 80s. Jim McCartney, segment manager for layout and BIM integration for Trimble says the company goal is to move BIM from the office to the field and vice versa. Knowing that contractors were an early and aggressive adopter of BIM technology, Trimble worked to move BIM model information toward seamless use in the field. In the past, contractors used tape measures to locate points—a slow and less accurate way of doing layout work.
Trimble and Tekla joined forces to electronically transfer BIM software files to layout equipment in the field and also send as-built information from the field back to the office. “This information exchange can either be e-mailed directly to Trimble's handheld computer or transferred via a USB connection from a computer,” says McCartney. The challenge was to convert a Tekla Structure's BIM model into a usable format that Trimble's field computer could recognize. “For example, if field personnel want to layout points for a footing, they cue up the footing model and all the needed layout data points are displayed,” he says. The object is to convey electronic information fast and accurately without additional human input. Change orders can be sent to layout instruments from the office too, seamlessly making changes that layout tools can recognize.
McCartney says the renovation of structures is approximately 30% to 40% of the construction market today. Starting with files generated by 3-D laser scanners of existing conditions, designers can import the data into BIM software to start the virtual design process. This backward flow of information also can be sent to designers or contractors at any point during construction to verify the models, and at the conclusion of a project for as-built drawing creation.
Contractor involvement with BIM
It's unusual for contractors to use design software, but they were early and aggressive adopters of BIM technology. “Because they are more visually oriented, they made a personal connection with BIM,” says Dickey. “They were also quick to see the cost-saving possibilities.”
Sundt Construction was an early adopter of BIM, starting a department about four years ago. Now, about 70% of its projects use BIM. Russell says they currently employ six full-time modelers and 25 project engineers to handle trade coordination work. “When we use BIM, there is better coordination among trades, a reduced amount of rework, improved productivity, and maximized prefabrication.” The point at which Sundt starts using BIM in the construction process depends on the type of contract. When working on design/build projects, which take up approximately 20% of Sundt's work, BIM modeling starts with the award of the contract. If it's an at-risk bid project, work starts after subcontractors are on board. It also depends on whether the designers for the project use BIM or not. Like SOM, Sundt uses a variety of software packages with strengths in certain areas to build its models, using Navisworks Manage to bring all the information into a common environment, at which point clash detection can be conducted. Russell says they prefer to work with subcontractors who use BIM on design/build contracts, and only partner with architectural firms that design with BIM.
It takes Sundt about six months to train personnel to use BIM effectively. Continuing education occurs offsite once a year for staff and through webinar programs onsite. He says Arlington, Va.-based Associated General Contractors of America's BIM Forum offers webinars that are very good.
Morley Construction, Santa Monica, Calif., who self-performs all its concrete work, started using BIM in 2006. It began with Revit software, doing an entire project including shop drawings. Today, 80% of its projects are constructed using BIM. Reginald Jackson, the company's vice president, says they are in the early stages of estimating concrete work using BIM. Morely Construction currently uses Revit for most drawing work, Navis for clash detection, and Navis Desk for viewing 3-D models. Jackson says they use BIM for shop drawings, 3-D representation, quantity take-offs, project phasing (4-D scheduling), and visualization for the whole project team. Morleys' field personnel also use BIM, and Jackson says it didn't take much training to get them started.
William Shebetka, formwork operations manager for Baker Concrete, Monroe, Ohio, currently uses Tekla and Revit—Tekla because of its concrete contractor focus. Baker currently uses BIM for understanding the structure, completing quantity take-offs, scheduling, and clash detection. He says one of their structural projects involves more than 500 concrete placements, and they are using BIM to figure out how all the placements will work together. Baker currently is looking into using Trimble and Tekla's technology link to do survey setup work on the jobsite and is discovering they don't need the same skill level on the job for this work.
Shebetka adds that future project engineers hired just out of college will be required to have BIM experience.
The construction industry is currently in a constant state of change. The old adage that you shouldn't build castles in the sky isn't true. BIM does indeed make it possible to build them in the sky—attaching them to the ground when the construction team starts work on a jobsite. Given that BIM has both a design and a construction component, you as a contractor need to start on this learning adventure. BIM pushes team-work and all parties of a project to join in on the discussion.