Monday, 24 September 2012

USACE and Level of Development

The US Army Corps of Engineers has recently released their Minimum Modeling Matrix or "M3" - available at cadbim.usace.army.mil. This document is a spreadsheet that contains three worksheets: Instructions, Modeling Requirements, and Scope-LOD-Grade.

Referring to a post on All Things BIM ("Moving Forward With LOD"), the USACE M3 document utilizes the AIA LOD definitions and classifies the built environment with a minimum level of required information from design and construction teams.

They did a nice job in categorizing the built environment their own way and then including references to Omniclass, Uniformat, AND MasterFormat. You can even filter the Scope-LOD-Grade worksheet in column A to show different level of specificity (as in Uniformat, Level 1, 2, 3 and 4).

LOD gets a 'Grade'

USACE has utilized only the 200 and 300 levels of development, and has limited use of 100. They specify the LOD in only one column and then they have introduced a concept of 'grade' as an additional qualifier to the LOD. Here's the explanation of the Grades according to USACE:
A = 3D + Facility Data
B = 2D + Facility Data
C = 2D Only (drafting, linework, text, and/or part of an assembly)
+ = Original grade (A, B, or C) adjusted for contract changes and field conditions
When you put the LOD together with Grade, you get an interesting interpretation of the original level of development scheme.
You can see in the sample above that within Fixed Furnishings, it would be acceptable to include Window Treatments in the model as generic-2D elements (200-B), whereas Casework must be specific-3D elements (300-A). To be honest, I'm not sure how I would model Fixed Art at 100-B...

Also note that Record Modeling and As-Builts are included in the USACE minimum requirements. The plus (+) symbol next to all There is often a question in our industry about the difference between the two and my opinion is as follows:

  • Record Model - Design model that has been updated with any recorded changes (usually via RFI or Change Order) during the construction process. The model is NOT updated with in-field conditions. This seems pretty straight-forward for geometry - much different when you're talking about data.
  • As-Built - Design model OR fabrication model that has been updated according to installed conditions. Again, if we're talking about data, that usually means serial numbers and other detailed information that would not be part of the design model.
At an Autodesk University panel presentation, the team from USACE clearly explained that they see the Record Model and the As-Built Model as THE SAME THING. Notice in the image above that the column heading is "RECORD MODEL (AS-BUILTS)." Remember this if you are working or will be working on a USACE project in the near future.

Modeling Requirements

The CAD/BIM team at USACE has also created a worksheet for "Modeling Requirements" that lists a very broad statement for each major building system - organized to Uniformat Level 2 specifications. This presents a potential 'scope-creep' situation for design teams in that the Modeling Requirements do not describe different levels of modeling specificity. This type of modeling specification is being examined by the LOD Specification Workgroup of the AGC and AIA mentioned in the All Things BIM article above.

Why is the Modeling Requirements table potentially dangerous to a design team's scope of work? Here's an example...if we look at D40 Fire Protection, the requirements are as follows:
"All Fire Protection elements including all piping, valves, and seismic bracing shall be modeled with necessary intelligence to produce plans, elevations, building/wall sections, riser diagrams, and schedules where applicable."
At a more generic level of development (200), an engineer would likely not include valves and seismic bracing; therefore, where do these requirements apply?

Conclusion

Overall, I applaud the USACE CAD/BIM team for their effort to point the AEC drivers in the general direction of travel - considering the AIA E202 was merely a road map. I hope they can refine their approach over time to allow greater clarity in a more simplified approach towards establishing minimum modeling standards. It will be quite exciting to hear about some project case studies as teams work with the USACE in the near future.

1 comment:

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