Selden B2 - BIM for Contractors

I ended up doing a lot of clash detection meetings with contractors on my second co-op, so I naturally found interest in the topic for my group this week - along with a fair bit of background and understanding.

Construction Firm Types 

The chapter starts out by stating the importance of contractors input to the BIM model during the design phase. In the most typical of construction, design-bid-build, the contractor doesn't have any BIM say until the design is already completed - simply coming in for their specific trade.
As you probably could have guessed, contractors get the most out of BIM when working in a design-build or Integrated Project Delivery (IPD) setting. Essentially where the contractor is considered in the design process from the beginning.

What do Contractors Need/Want From BIM?

As a synopsis, the ideal BIM model would include:

• Detailed building information 
• Temporary components (scaffolding, equipment, etc)
• Specific information for each building component
• Performance and project requirement data
• Design and construction status

Any single modeling program we have today would only accomplish roughly the first two on its own. Each of these requirements is necessary for full incorporation of planning and execution of a project.

BIM modeling becomes really useful when importing all trades for clash detection, especially in regard to vertical spacing - an aspect that can be difficult to grasp from overlaying 2D drawings.

After reading this chapter it has become apparent that the most important (if any) is having detailed information entered into the model; without complete accuracy here, clash detection and other uses thereafter only have partial accuracy.

Different ways BIM is Implemented

There are two primary ways a BIM model is created and used during a project, illustrated by the flow charts below (figures 6-4 and 6-5 in the text).

The first chart is a process where the contract takes all the 2D drawings and combines them into a 3D or BIM model. From there the models can be used for take offs, scheduling, etc. The problem with this method is still the lack of communication between the parties. 

The second method is more favorable as it provides more communication by ending in a shared 3D/BIM model.

At the end of the modeling process, the quantity and measurement information is imported to a extimating program (most commonly Excel) to perform an accurate overall estimate. It can also be brought into a 4D CAD model, where the 4th dimension time for smoother scheduling and visualization of temporary equipment.

In My Experience/Opinion 

Having the contractors input it crucial to BIM, but also any type of trade specific plans. The contractors and subs are the ones with the knowledge about their trade, and the only ones really capable of dictating what is possible to construct. 

Every week on our job site we would have a meeting with the subs and super to go over the upcoming clashes. And just as the chapter also mentions, every time one clash was solved, it inevitably caused multiple others. 

Overall, BIM has greatly simplified the process of trade coordination and error detection, but it still has a way to go before becoming an all encompassing method.

Sources:
[1] BIM Handbook: A Guide to Building Information Modeling for Owners, Managers, Designers, Engineers and Contractors (Wiley, 2011)

Responses

Ronaldo  - It was also referred to in my chapter that BIM had been initially created in the 80's. I'd be curious to see what that would look like. I also find it interesting that the first few uses, so it seems, were in movies, and it wasn't until later that it became advanced enough for building modeling.

Peter - I like that you refer to owners constant want changes to the project, I'm sure we can all relate to that. I agree that BIM really helps show the implication of these changes. In my chapter about BIM and contractors, it was stated multiple times the necessity for inclusion of the contractor in the modeling process, which I believe would further help owners with understanding - having the potential  for issues to be explained by an expert.

Taryn - I also agree with Eastman when he comments on the intuitiveness of Revit. The way it was been designed to specifically draw a wall, door, etc. with the included properties, takes it above the simple lines that CAD gives. As you also mentioned, the ability to import and export into so many other programs makes it a very diverse tool.