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The building industry continues to debate what constitutes BIM and whether the method reduces project risk.

In its most simplistic form, BIM is a 3-D model with information associated with the objects contained therein. In its most complex form, it is a multi-disciplined process among all project participants. Architects were the first to see the value in creating 3-D models to win business. Design engineers use models to flesh out the building in more detail and confirm their structural integrity. In many cases, the model never progresses beyond its use as a design tool, or what is often called “design” BIM.

While design BIM serves an important purpose, “constructible” BIM has proven highly effective in risk reduction because it contains all of the project details necessary to build the structure—right down to the position of each anchor bolt, the length and placement of each piece of rebar, and much more. When used to its fullest potential, every member of the team will rely on the model throughout the construction process, making even the largest, most complex project much less risky.

It stands to reason that project risk can be reduced with a higher level of planning, coordination, information and communication. General contractors and subcontractors that work with a 3-D model can expect to substantially reduce the risk of schedule and budget overruns, project changes, disputes and safety issues derailing the job.

1. Schedule
When projects are planned and visualized in great detail, with every stakeholder having documented input, it’s more likely that the construction phase will progress as forecasted. Being able to order materials to exact specifications for a specific delivery date helps ensure the project isn’t delayed due to a shortage or miscalculation. Being able to fix problems in the model prevents having to make adjustments in the field that can throw off the schedule.

The model also helps speed up the review process. For example, North Carolina-based concrete contractor Wayne Brothers reported being able to review rebar placement in the 3-D model of the Sierra Nevada Brewery in Fletcher, N.C., for accuracy and have the steel fabricated and shipped to the jobsite in just two weeks—or twice as fast as it would have taken the firm if it had been working off 2-D drawings.

2. Budget
Everyone wants the job to come in on budget, but the real trick is having enough information to calculate the cost of a project accurately, thereby reducing the contingency factor to produce a more competitive bid. The detailed information contained in a 3-D model can be used to produce more accurate estimates and reduce cost overruns due to unreliable manual material orders and the cost of correcting errors made during construction.

On the Sierra Nevada job,3-D modeling was exceptionally valuable for a bridge that needed to be built on the road to the brewery. The bridge had been designed based on a 50-year-old aerial topographic map. Only when Wayne Brothers integrated the bridge model with a newly created 3-D model of the creek bed scan did it become apparent how inexact the bridge design was. A quick redesign allowed the contractor to order the correct amount of rebar, thereby reducing waste and resulting in a more coordinated, efficient project without any rework.

3. Changes
Even a model containing all the construction data for a job won’t prevent changes from happening; it’s part of construction. However, one of the benefits of using a model is that changes can be made rapidly and immediately shared with all project team members, including those on the jobsite. Whether viewing the model on a computer at headquarters, in the jobsite trailer or on a mobile device, everyone is assured of having the most recent information.

4. Disputes
When all parties are contributing to and working with the same 3-D concept, problems are much more likely to be resolved before ground is broken, dramatically reducing the likelihood of a dispute over design intent and interpretation. Moreover, design and engineering flaws can be discovered and corrected before time and money is spent on construction.

5. Safety
Safety is the foremost priority of any building project. While incorporating safety functions into 3-D modeling has lagged behind other features, the potential to use technology to improve construction is promising. For example, Georgia Tech is developing tools that can be used to analyze a 3-D model and assess safety. If penetrations in slabs are large, the software automatically generates barriers around it; any exposed edge of a slab above ground level will equally receive a barrier. Although not yet commercially available, this tool is a good example of how 3-D modeling could be used to improve safety.

BIM gives general contractors clarity about building projects with an opportunity to correct potential problems before breaking ground. Everyone involved benefits from having precise, actionable information that improves planning and execution to reduce risk and keep projects on schedule and within budget.

Alistair Wells handles business development for Tekla, a Trimble Company. For more information, call (877) TEKLA-OK or visit www.tekla.com.

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