Using BIM for project coordination

BIM is used frequently when working across multiple disciplines, which can prevent clashes across mechanical, electrical, plumbing, and fire protection engineering and with other stakeholders.

04/24/2017


This article is peer-reviewed.Learning Objectives:

  • Understand the basics of BIM for project coordination.
  • Compare clash prevention and clash detection; identify where each is best used for BIM coordination.
  • Illustrate how BIM can improve workflow and overall engineering design.

Building information modeling (BIM), clash detection, clash prevention, level of development (LOD), 4-D, 5-D: These are terms heard or used regularly by those working in the architecture, engineering, construction (AEC) Industry. But at the rate these terms are thrown around, do we really understand what they are? Are we really doing what we say we’re doing? If we aren’t, why aren’t we? Are we following best practices?

Many engineers assume that if they’re using Revit, they’re doing BIM. However, although Revit is one of the many tools to use for BIM, many individuals only use Revit for 3-D modeling—and they may or may not be coordinating among disciplines. Three-dimensional modeling is only considered BIM when information is tied to what is modeled; that is, when elements in the model have data in them that is scheduled on drawings or used for cost estimating, exported for other tasks in construction, or even used for facilities management.

Clash prevention versus clash detection

Figure 1: A coordinated mechanical room is modeled to a level of development (LOD) 300. At an LOD 300, all piping, equipment and other items are modeled at actual size, quantity and type, which is necessary for proper coordination. All graphics courtesy: CannonDesign

When it comes to using BIM coordination to determine where elements “fit,” there are primarily two processes of coordination: clash prevention and clash detection.

Clash prevention provides assurance that the modeled geometry of all building components and systems will fit in their allocated space and that all items can maintain access and serviceability. This process is primarily done during the design phase when laying out the routing of all systems. While not every offset or adjustment is shown in the model for design documentation, the building can be constructed without issue, and any adjustments not requiring a request for information (RFI) are made by the contractor during the construction phase.

Most clash prevention tasks on a project can be performed simultaneously while developing the design, but require each individual on the project team to do due diligence of coordinating any congested areas of the building. While designers are working in a model, some critical areas may still require communication among team members, whether it be face-to-face, over the phone, via email, etc.

The clash-detection process is a review that ensures all building components, assemblies, and systems properly fit in their to-be-installed condition without interferences or encroachment with any other building assemblies. This process is occasionally done by the design team if required; however, this is often done on the contracting side. Several ways clash detection can be accomplished include, but are not limited to:

  • Interference check reports in Revit
  • Clash detective in Navisworks Manage
  • Model checks by visual inspection in 3-D coordination views.

The interference check tool in Revit has received some improvements recently, allowing for easier coordination checks. Within the tool, element categories are selected to compare against other elements in the model or with elements in other linked models, such as inspecting for clashes between structural steel and plumbing piping. After the report is run, elements that have an invalid intersection (collision) are listed, with both element ID number and a descriptive name ID. These can then be selected and shown in an available view to adjust. Using this method can be quicker than performing clash detection in a separate program, however, using a program like Navisworks for this may be better performance-wise for those using computers with less horsepower on larger projects.

Clash detection in Navisworks is probably the most well-known option when it comes to BIM coordination and is very popular on the contractor side. Navisworks can handle many different file types and is typically quicker to use than an equivalent Revit model. Search sets can be used for filtering or color-coding the various systems in a model, and clash detection is relatively easy as well. During the coordination process, clashes can be found in the Navisworks model and updated in the Revit model. These updates are done manually in the Revit model; however, Autodesk does have a tool called switchback, which allows users to quickly move back and forth between the Revit design and Navisworks review models.

Figure 2: Using Revit’s interference check tool allows an engineer to quickly find any invalid intersections that may have been missed through other coordination methods.

Coordination views that are predefined in the Revit model are easy to use for both clash prevention and clash detection. These can include 3-D views, sections, and working views that are double-line (fine detail level of graphics) as well as color-coded with filters applied to the various systems. These views are regularly used throughout the design of a project and can be used in coordination meetings instead of the old “paper tacked to the wall” method, which usually still results in some coordination issues.

Another type of coordination or working view in Revit that is valuable during design is the structural plan view. These views are used to see where the beams or foundations are located that support the level being viewed. With these, it is easy to coordinate the location of floor drains, fixture drains, or any other floor penetrations.

LOD specification

The LOD, while sometimes referred to as the level of detail, is actually the level of development specification. This is a reference used in the AEC industry to standardize the level of quality and reliability of content in building information models at various stages of the design and construction process. This specification receives annual updates and review by BIMForum, the U.S. chapter of buildingSMART International. The LOD in a model has a direct connection with coordination in that model, and using the BIMForum LOD for your company’s standard level of detail is best for collaboration with other firms or contractors on the same project. For clash detection or even clash prevention, a minimum of LOD 300 is required. At an LOD 300, all piping, equipment, and other items are modeled at actual size, quantity, and type, which is necessary for proper coordination.

When agreeing on the LOD for a project, it is better to think about what level the project is required to be at for completion, rather than what is desired at each phase. While an LOD 200 (in which most content is generic in size, shape, or type) may only be needed for an earlier phase of a project, sometimes it makes sense for some content to already be at an LOD 350 (where content is true to size, shape, and type and may have embedded information).

For example, at the design development phase of a project, the requirements may be to provide an LOD 200. However, the water heater may have already been selected, so an LOD 350 is used to place the water heater graphically in the model. Also included at a LOD 350 is the parameter information that is automatically populated in the water heater or equipment schedule, which in turn is needed for the design development submission. For this reason, it is better to view the required LOD for each phase as a minimum rather than as a required “target.”

Keep in mind, the LOD for a project is usually specified in a project’s contract and BIM execution plan, where many firms have an LOD to which they typically design projects. However, some projects may have circumstances requiring a different LOD from the norm, so it is helpful for this information to be communicated to team members during a project’s BIM kickoff meeting where all model-related information is shared with the project team.


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