Understanding BIM—4D Scheduling
May 18, 2010
In theory, BIM (building information modeling) offers multiple benefits for contractors, ranging from the very basic tasks of 3D visualization and clash detection, to the more advanced functions associated with 4D scheduling and 5D estimating. On average, you tend to see more visualization and clash detection success stories than you do anything else when it comes to BIM. But a few companies are looking to buck that trend.
The 4D schedule allows contractors to link objects that are in a 3D model to the corresponding tasks and activities. This produces a visual representation of a timeline, which will allow contractors to do clash detections between trades while also comparing planned versus actual schedules. This means conflicts can be resolved before the project even begins.
In addition, the 5D estimate allows contractors to visualize projects in a similar way—as it relates to cost. In many cases, 4D scheduling and 5D estimating have saved construction companies a considerable amount of time and money. In the case of the 4D schedule, contractors can prevent potential schedule conflicts.
One example is Mortenson Construction, www.mortenson.com, Minneapolis, Minn., which used a 4D model to identify a potential problem in the steel sequence on a hospital project. The model identified an area of the steel erection that was scheduled before there was steel below.
According to the company, without identifying this conflict the project would have had an extended timeframe and additional costs, due to downtime of steel workers and the costs of cranes onsite that aren’t being used. Currently, the project is on schedule for a June 2011 completion and the project remains on budget.
Turner Construction Co., www.turnerconstruction.com, New York, N.Y., recently broke ground on a new research building for a nationwide children’s hospital, which is scheduled for completion in 2012. Turner is using BIM to visualize the design, coordinate the construction, and analyze and track the progress. Specifically, the company is using 4D schedule analysis.
While larger general contractors are using the 4D schedule in the BIM process, specialty contractors are also looking to this process to enable construction to be completed on schedule and on budget.
John Rapaport, general counsel and director of operations, Component Assembly Systems, www.componentassembly.com, Pelham, N.Y., says the company is looking to better leverage all systems it has in place, and this includes 3D, 4D, and 5D BIM.
One of the specific areas Component Assembly Systems involves tying the model to the schedule. Of course as a specialty contractor, the company is also looking to build models using tools that are specifically related to the wall and ceiling industry.
Rapaport says, “The continued involvement of the (foremen) in these efforts to bring out our best means and methods and get us ready for design-assist work early in a project (helps) enable more company sales and transparency in design and our sequencing of operations.”
While this is just one aspect of the entire BIM process, contractors are finding 4D scheduling can help save a significant amount of time and money, while also reducing conflicts.