Using Revit Structure for More Than “Revit Structure”
Introduction
Contrary to what we would like to believe, the construction workflow is not as clear-cut and simple for the average individual to understand. The devil is in the details. What!!? Say it ain’t so!
OK… let me step back a little. Yes, throughout its lifecycle a project will follow a clear progression from design to construction to occupancy. The key is using virtual design and construction technology (VDC) to help the overall process in minimizing the loss of information in the hand-offs between the phases and enhancing communication between the parties involved.
Let’s face it. The overall construction process from start to finish is not as efficient as it can be. Furthermore, inducing technology in this inefficient practice can sometimes be more detrimental as technology itself is disruptive.
Mike Tyson said it best: “Everyone has a plan until they get punched in the mouth.” Whoa... I’m not implying that you punch someone. Take a deep breath. Ok…
What I am trying to say is that what complicates issues on projects is when a project encounters changes during design or construction. (It’s like getting punched in the face... multiple times.) On large technically challenging projects (i.e., hospitals), the ability to manage the construction schedule becomes dependent on the project teams’ ability to manage changes. This is where precisely effective communication can make or break the job.
Let’s take imaging equipment on a hospital project, for example. A change in an equipment vendor late in construction can be a huge hit to a project (especially a hospital project in California where you have to worry about OSHPD). What is OSHPD you say? Uh.. let’s leave this topic for another day. In general, it’s a regulatory agency, and a quick Google search can provide you with all the answers.
Changing a piece of equipment late in construction undoubtedly means redesign and re-coordination. As change directives are issued, the designers’ Autodesk® Revit® models get updated to reflect the latest architectural room and structural details. These models generally get shared with the general contractor to support the 3D coordination process and vetting of design intent and to-be installed elements.
However, to truly support coordination and keep up with the pace of construction, further modeling is carried out to bring it to a sufficient level of development and incorporate vendor-specific constraints that drive the location and type of contractor installed items.
All right! Now that I have laid the ground rules, let’s examine this a little more closely.
Equipment Coordination
Imaging equipment is probably one of the most critical and expensive aspect of any hospital project. The challenge that we typically face is from the time the building gets designed to when a piece of equipment gets procured, the technology has advanced and the equipment that was specified is no longer the latest model. As medical imaging technology is continually evolving, the owner often seeks to wait until the last responsible moment to select the equipment type and vendor to ensure maximum longevity and performance. This following example hospital has seen a major change in equipment vendors mid-construction, which has caused a large portion of the ground level to be redesigned to incorporate the new vendor-specific constraints and user inputs.
Considering the ground level slab was already poured (minus left-out areas of the MRIs to account for any magnetic or radio-frequency shielding), the layout of anchors and trenches in the left-out portions of the slab have to compete with atypical rebar configurations, including areas requiring additional trim to tie into existing slab dowels or rebar leave-out areas dictated by the vendor. (So basically, quite a bit of coordination is still left to be done while the project is in construction.)
Design Model Helping Construction
As most of you know, the isocenter[1] is probably the most important point to get right in a room as it drives the entire layout and ancillary equipment placement. This point is typically referenced in drawings as a simple annotation in plan view.
You can change that and represent it as a cylinder 3/128” in diameter (smallest allowable extrusion in Revit). Having it clearly identified in a 3D model format as opposed to a 2D annotation allows us to use it during the coordination process in Navisworks® as a reference object. This further allows you to identify subcontractor minimum distance requirements.
Tip: An easy way to extract just the isocenter geometry is by selecting all instances of the family, grouping the objects, and linking the group back to the project model. A separate file is created that can be used with just the information needed.
Figure 1: Using group linking to quickly extract 3D information from large models
Anchors
In order to review and coordinate the anchoring requirements (set by imaging equipment vendors) and the structural engineer of record (SEOR) against the rest of the trades and the existing slab conditions, the previously created model is now populated with anchor families tailored to the various equipment vendors.
Although the vendor design documents specify the location and load to be considered for anchorage, the SEOR specifies the type of anchor to be used, the embedment, and the edge distance requirements.
Using Hilti’s BIM library[2] (freeware), the anchor families were created for each vendor in separate Revit families. Anchor families are then placed, aligned (using the align command), and locked in place to the isocenter “family” in Revit.
Are you with me?
Aside from just managing the file size, now the 3D modeled anchor elements are locked to isocenter family in the main model and will move along with any modification made to that model. This eliminates the risk of coordinating around anchor locations that did not update if changes are made to the isocenter location.
Coordination Anchors, MEP Systems, and Existing Slab Conditions
Now that we have the anchors and isocenters modeled, the contractor’s Navisworks coordination model can be refreshed with specific clash detection batches (with a clearance value equal to the distance requirements for each anchor type).
The anchors’ location is also coordinated with the existing slab rebar to ensure the anchors can actually be installed where they should. If the slab will be poured months prior to this installation, the team can laser scan the rebar before concrete poured. The point cloud (in .rcs format) can be linked in Revit showing the rebar location, though it is recommended that you coordinate anchors and rebar directly in Navisworks as it is faster and easier to identify conflicts.
Caution! You might have to talk to your contractor here.
Tip: In Navisworks, select “Navisworks View” in the drop-down for the Revit file format import option to convert only the Revit view containing the word “Navisworks.” This helps maintain control over what Navisworks has to work with.
Figure 2: Specifically rename one of your Revit views to have better control over what Navisworks loads
Figure 3: Diagram describing the creation of the Contractor Revit model and its use in coordination
Conclusion
OK… let’s wrap this up.
Building projects are constantly changing and evolving during design and construction. Revit is a very powerful tool that sometimes only gets utilized to a fraction of its potential. Talk to your friendly neighborhood contractor to collaborate and think of ways to use Revit other than just for producing 2D documents. This will help other players down the line and avoid some of those pesky RFIs from stagnating on your desk.
3D parametric elements are “wicked” smart. Let’s not dumb this information down to flat 2D sheets of paper.
Use Revit Structure to manage structural modifications due to medical equipment changes instead of being in reaction mode. Like Mike said, don’t get punched in the face.
Jean Goyat graduated in 2010 with a Master’s of Science in Engineering from the Ecole Centrale of Lille, France and in 2012 with a Master’s of Science in Construction Engineering and Project Management from the University of Texas at Austin, researching the application of 3D and 4D modeling on large highway projects. Jean is an Autodesk AutoCAD, Revit and Civil 3D certified professional, putting his knowledge of the Autodesk suite and other software to use in the building industry for several projects over $500M in the San Francisco Bay Area, focusing on design coordination along with the use of 4D models for constructability and logistics as well as data integration and database development.
Kaushal Diwan is a BIM Manager and leader in implementing BIM at DPR Construction. Kaushal also leads DPR’s corporate BIM training program and supports project teams across the nation. Kaushal is passionate about establishing a highly efficient BIM approach within multidisciplinary networks and is the founder of the “Sacramento BIM Network”; a group of Sacramento BIM professionals focused on information exchange in the construction industry. His eight years of experience in the industry consists of BIM implementation and cost estimation for technically complex projects. His project experience varies from a 400,000 square foot healthcare facility to higher educational LEED buildings to the new 420,000 square foot Sacramento International Airport Terminal B. He is actively involved in national and local BIM groups and has been a popular speaker at Autodesk University, local colleges and universities, and within the Sacramento Architecture, Engineering and Construction (AEC) Community.
[1] The intersecting point of the axis of rotation of the gantry, the collimator, and the treatment couch
[2] http://download.hilti.biz/data/techlib/bimcad_lib_revit/HiltiBIMCADLibraryRevit.exe
