This week my group was instructed to read Chapter 2 of the BIM Handbook. It's entitled, "BIM Design Tools and Parametric Modeling" . The chapter is intended to compare BIM design applications and previous CAD systems. According to this handbook, 3-D geometric modeling has been a hot topic since the 60s. Several fields were interested in this practice including architecture, engineering, film, etc. Many recognized that 3-D modeling could be utilized in a wide variety of applications. The first successful representation of polyhedral forms (seen in the film Tron) was produced through a limited set of scalable shapes defined in terms of parameters. Over time much progress was made and solid modeling soon emerged. Two major methods existed: B-rep - which defined shapes as a closed set of surfaces - and swept shapes (which reminds me of the many models we made in Pro-Engineer as part of ENGR 100) - which defined shapes as revolutions of a figure about an axis. After taking the reader on a journey through the very beginning of parametric modeling, the author notes some capabilities of parametric modeling that have been left out of most BIM software. He also raises the point that parametric object modeling is key for easily editing geometric shapes, which makes me wonder, "how efficient is current modeling technology if some capabilities have been left out?"
The author almost immediately answered my question by addressing the current generation of BIM design tools - most of which I'm familiar with. Apparently Autodesk Revit and Bentley Architecture were created based on the object-based parametric modeling capabilities originally purposed for the design of mechanical systems. Eastman also provides a helpful explanation of parametric design as it applies to architecture, "Instead of designing an instance of a building element like a particular wall or door, a designer first defines an element class or family which defines some mixture of fixed and parametric geometry, a set of relations and rules to control the parameters by which element instances can be generate." When this technique is utilized, shapes and elements will be adjusted according to its relationship with surrounding objects (distances, angles, etc.). While traditional 3-dimensional CAD requires the user to physically make each of these adjustments, changes will automatically occur in newer BIM software. I've always wondered why Revit's user experience was so different from regular AutoCAD. After reading this chapter, I now understand. The very logic behind the respective design methods are much different.
Not only can this software be used in the design phase of a building, it can also be utilized for construction and fabrication purposes. This affects not only the architectural system but also structural, electrical, plumbing systems, etc. While these applications have yet to be perfected (companies are working to include construction material associations for more accurate modeling), they do show great promise for BIM.
Another passage that stood out to me described BIM's pros and cons. The greatest benefit listed is "the intelligent design behavior of objects". Eastman describes the automatic editing as "one's own design assistant". Despite BIM's many advantages, there are also some limitations. Systems designed by the software are inherently complex and involved many parts. For this reason, employee training can take a lot of time and will thus be costly.
Overall, BIM is a really exciting tool. It reminds me of all the other advancements I researched for last week's post. Semi-automatic technology is clearly the way of the future and BIM is no exception to the rule. It's exciting to hear all that can be done and I look forward to learning more about it and increasing my proficiency.
Eastman, Charles M. BIM Handbook a Guide to Building Information Modeling for Owners, Managers, Designers, Engineers, and Contractors, Second Edition. 2nd ed. Hoboken, N.J.: John Wiley & Sons, 2011. Print.
Comments
To Jonathan Plotkin: The table you posted was extremely informative. My mind was drawn to the story Dr. Mitchell told us in class about the shift in staffing when CAD became popular. It was extremely interesting to notice the decrease in intern architect project hours, the flip flop of work hours between project architects and level 1 architects and the fact that principals weren't event affected (which makes sense). I thought it would be more profitable to train less experienced employees in the ways of BIM as opposed to increasing hours of more experienced employees but I guess it's not.
To Hang Wang: I really enjoyed hearing about the application of BIM in the construction world. Most of the time when it's discussed, we're talking about its effect on the design phase. I'd love to learn more about the "clash detection" you mentioned.
To Ami Amegan: I was surprised to learn the effect of BIM on an owner's involvement in the construction process.I believe BIM is an excellent way to bridge the gap between designers, contractors and owners - who constantly operate in separate worlds (from my personal experience). It's great to have a tool that can bring everyone together AND reduce costs while doing so.
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