During a BIM project, model data from consultants, designers and subcontractors is compiled together.
This process is usually referred to as federation. There’s always an argument about the definition of this term, I’m just saying that it’s what most people I’ve worked with call this process.
Federation happens for various reasons – it’s required for clash detection and other forms of analysis. It is also needed to achieve 4D, 5D and 6D BIM requirements – construction simulations, QS examinations and use in FM/ops.
I’d like to demonstrate a potential problem when federating, and suggest a few methods to prevent it from happening…
Duplication of geometric data
Below are some examples that I regularly come across:
Two (or more) identical components occupy the same space in the model. This can be hard to spot (here they have been highlighted in different colours to make it obvious).
Floor slab example
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Column example
Something like this has happened:
All consultants submit construction drawings derived from their BIM data. For these drawings to be useful, ‘placeholder’ building data from outside a consultant’s discipline is added to the model.
The date for sharing BIM data arrives and the entire model (including these ‘placeholder’ components).
During federation the BIM Information Manager (or whoever) doesn’t notice there are duplicated components, and during analysis one or more of the following problems occur:
- False issues during clash detection.
- Incorrect QS areas/costings.
- Incorrect information take-off for schedules.
- Incorrect COBie/FM data.
Each of these problems has a real time or cost impact on the project, so we must try to avoid this.
1. Filter your model before sharing
Turn off components that another consultant is responsible for. If you’re using something like ArchiCAD you can do this through layer combinations. If you’re on Revit you can use Visibility/Graphics options.
For this method to be successful each consultant must understand their modelling responsibilities or you end up with missing components. Users must also remember to jump through the same filtering hoops every time BIM data is shared.
It is essential that the project’s BIM Execution Plan (BEP) contains a responsibility/LOD matrix and that it is properly enforced.
