Building Information Modeling (BIM)

What's the BIM Deal?

25 Aug, 2009 By: Robert Green

Understanding building information modeling begins with sorting out fact from fiction.

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If you're at all into CAD you've seen the acronym BIM, short for building information modeling, all over the place the past few years. If you're a CAD manager in an architectural environment you're probably starting to plan for, or even test, BIM technology. If you manage CAD in the construction or building engineering trades your senior management may be asking you how BIM is going to change your company's approach to modeling in the coming years. Even civil engineers are scratching their heads over how they'll integrate BIM models into their site planning databases. It seems only those who do machinery design are immune to the long tentacles of BIM.

So what is all the fuss about? How might BIM affect all of us who manage CAD in the AEC environment? These are good questions, and I plan to explore all of them in the next few issues of the CAD Manager's Newsletter. Here goes.

The Basics: Deciphering the Hype
Any time a new type of software hits the market, a tsunami of promotion is unleashed that paints the trend as the greatest thing since sliced bread. The introduction of BIM has been no different in this regard, with all manner of promises of "ease of use" and "higher productivity" touted without much data to back up the claims.

So how can we separate all the hype from the fundamentals we need to understand to implement and manage BIM technology? To answer those questions, we'll need to learn what BIM can do for our companies, define what the limitations are, and gain a solid understanding of the resources required to deploy BIM.

What BIM Can Do
BIM is building design in 3D — and more. The building information model encompasses all data associated with the building design, including geometry and geographic information and quantities and properties of building components.

Ask five different CAD managers what BIM can do, and you're likely to get five different answers. (And I'm sure I'll receive a good bit of e-mail after I set out my own vision of BIM!) So, for the sake of starting the conversation, I'll lay out the various categories of BIM I see in the marketplace now, along with the core functionalities those products bring to the table.

Architectural BIM. A high-end 3D CAD tool that captures the geometry of walls, foundations, frames, roofs, and window systems of a building. By capturing the properties of the building (glass properties, typical insulation values, etc.) and the climate zone information (based on where the building is located), basic energy computations become possible for passive solar heating, minimization of cooling loads, and optimal building placement to reduce building energy consumption. Most BIM tools also include visualization capabilities for pseudo-realistic rendering of projects as they take shape.

Structural BIM. Takes architectural BIM a step further by allowing the detailed modeling of structural beams, supports, and trusses along with placement of building loads for all the elements of a building that place weight on the structure — think steel members, concrete, equipment, furniture, etc. — to qualify the building structure for load compliance.

BIM for MEP (mechanical, electrical, and plumbing). The ultimate extension of the BIM analysis, since everything from water systems, hot water units, sprinklers, lighting, electrical conduits and trays, and circuits can be fully designed inside the building (BIM) model. BIM systems for MEP are relatively new and, thus, are in the greatest state of flux at present.

Unified BIM Theory
All BIM software tools facilitate the production of 2D construction documentation as a byproduct of the 3D models. Obviously, the type of 2D documentation differs as architectural elevations and reflected ceiling plans aren't the same as conduit and cable tray drawings, but the concept is the same. Like mechanical 3D systems, BIM uses the value proposition that once the building is modeled in 3D the 2D prints are a byproduct of the model.

In other words, BIM is simply a way to aggregate all the information we know about a building into a unified CAD software system instead of a bunch of disparate computer tools. So rather than drawing 2D building floors and elevations in a CAD tool, then performing structural analysis in another tool, electrical computations in a spreadsheet, and energy calculations in yet another platform, BIM seeks to unify the process in a single software environment.

I've read a lot of dissertations on what BIM is, but I believe my summary outlines BIM's potential in a lot fewer words with a lot less hype. (You may even want to pass along these descriptions to your senior management teams if they're asking you about what BIM can do.)


What BIM Is Not
I'll go ahead and make a few statements here that counter the marketing claims you'll likely read about BIM tools.

  • BIM isn't an AutoCAD or MicroStation upgrade.
  • BIM isn't something you install over the weekend then start using on Monday.
  • BIM doesn't design buildings by itself.
  • BIM doesn't make architects or engineers obsolete.
  • BIM tools don't install and manage themselves.
  • BIM tools don't have a "magic button" that automates implementation.

What BIM Requires
More software. And that software is more expensive than the simple AutoCAD or MicroStation licenses that have carried most of the 2D architectural workload since they replaced pencil and paper 25 years ago.

Better hardware. You won't want to run a thorough energy balance computation on a 3D building model on that old 1.8-GHz single-core Dell in the spare office. For big models, you'll need multicore machines with loads of RAM on 64-bit OS platforms.

User training. Just as 2D CAD didn't replace paper without a lot of user training, BIM won't replace AutoCAD or MicroStation without user training either. BIM is different from 2D CAD and users need time and training to make the switch.

Active management. If you install BIM tools in your company and turn everyone loose without any coordination, standards, or management philosophy, you're going to have a huge mess on your hands in short order. As a CAD manager you need to be intimately involved with how BIM will be implemented and standardized.

A file format strategy. Even if your company has gone all BIM all the time, that doesn't mean the rest of the world has. You'll need to collaborate with a variety of vendors who will most likely use industry-standard DWG files to convey information. How will you translate information to and from partners who aren't using BIM?

New attitudes. To move your company from 2D CAD to BIM, your users must embrace a different way of working. CAD managers know that attitudes don't change overnight, right?

Summing Up
Now that we've defined the basic parameters of BIM and some of the problems BIM can bring, it is time to get ready to manage the transition. Over the next couple of issues we'll do just that by delving into the topic areas we've outlined in this issue and using reader feedback to address key questions. And while getting a BIM strategy in place isn't easy, it is a process that can be managed. I welcome your feedback and questions as we go along.

And don't forget to participate in the CAD manager's mini-survey on how current economics are affecting CAD managers at

Until next time.

About the Author: Robert Green

Robert Green

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