Tuesday, January 31, 2017

BIM Planning and LoD

For members not familiar with BIM planning, it is the process of developing and documenting the various responsibilities of the stakeholders involved in a BIM project.

As defined in the Penn State guide, the stages of BIM planning are:

  • Identify BIM Goals and Uses
  • Design the BIM Project Execution Process
  • Develop Information Exchanges
  • Define the Supporting Infrastructure for BIM Implementation


Level of Detail vs. Level of Development

The LoD concept was developed by VICO Software for construction cost estimation. Faced with the problem of determining how accurate, or how definitive, were the model elements to which they wished to assign costs, they developed the concept they called "Level of Detail".

  • LOD 100 meant not very definitive (an area or volume rate is accurate enough)
  • LOD 200 assume the number of items in the model is correct, but use an estimate for each,
  • LOD 300 items are identified and actual cost can be used,
  • LOD 400 is a measure what has actually been supplied so can be used to assess payments.

In developing E203, the AIA decided to apply this system to all uses of a BIM model, from energy analysis to 5D programming. They renamed it "Level of Development" as an indication of the decisiveness of the information, because "Level of Detail" could get confused with the amount of information.

The LoD challenge

The purpose of an LoD table is to tell stakeholders what information they CAN USE. It is a measure of the certainty, or confidence, of that information. LoD typically varies according to project stage - but not always. LoD requirements may also vary among different BIM uses, to be recorded in the BIM plan, and appended to consultant and owner agreements, so that all project participants understand their responsibilities.


In the templates provided by Penn State, the Model Definition (MOD) table provides a breakdown of model elements against project stages. The author of each model element is recorded here, with attention given to when certain elements are handed off to others.

The Information Exchange (IE) table lists the same model element breakdown against the various BIM Uses that have been previously defined in the plan.




The first time I encountered this task, I admit to having the same incredulous reaction as BIM blogger Antony McPhee:
McPhee:
"Are they serious when they say every model element type has to be listed with it's own author and LOD? And use Uniformat or Omniclass or Masterformat? It is not just the massive amount of work to do it, who will ever refer to it? Do they really think the mechanical engineer is going refer to it to find out if he has to model duct work because some-one else might be going to do it?"
~

When I noticed the announcement of LOD Planner, I was intrigued. Clive Jordan was with VICO when the LoD concept was developed. His recent work with "a large real estate owner" provided the inspiration for a tool that would simplify this arduous task. In his case study:

  • 53% fewer clashes compared to the control project
  • 98% of constructability issues solved vs only 31% on the control project
  • 2 month saving on project duration with a higher quality output.

Sometime in our near future our BIMs (models and data) will become the primary deliverable for building and development projects. Owners will insist on receiving their data in a form that is useful and reusable.

The South Coast Revit Users Group will convene on Thursday, February 2nd, featuring a presentation of LOD Planner by BIM pioneer Clive Jordan.

To RSVP go to scrug.anyvite.com

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