This week, my group was assigned to read Chapter 2 of the BIM Handbook located in the Drexel Web Library. Overall, this chapter wishes to differentiate BIM design applications from other CAD applications. Many people think that come CAD systems are considered to be BIM, but most aren't. BIM includes much more information about an object than just its geometric and physical properties.
3D Modeling began as solid modeling and used simple shapes such as cylinders, blocks, spheres, and planes. Today, shapes can be created with much more detail and much more realistically. The main programs that include BIM today are Autodesk Revit and Bentley Architecture. These programs require user-defined values but also have fixed values within the system. Instead of drawing a door every time it is needed, a door family is created which contains many parameters like material and size. There are also a set of rules for each object like the amount of space it needs to be placed. There are families for everything including walls, windows, ductwork, piping, plumbing fixtures, and more. In this chapter, they described BIM tools as "object - based parametric models with a predefined set of object families, each having behaviors programmed within them." I thought that this summed up BIM tools very well.
One great aspect of BIM design tools that is different than regular CAD systems is the ability to explicitly represent the space in a building. The shape and volume of the interior of a space are extremely important to keep in mind and weren't represented very well in previous CAD systems. Things like the the space between floors that contain HVAC, electrical, and plumbing equipment were hard to describe without BIM. With BIM, these things can all be laid out more successfully. If there isn't room to put a pipe or duct, the program won't allow you to put it there. This is something that was definitely helpful for me when I was on my co-op working in the HVAC department with Revit. It is extremely helpful to be able to model the building with all different systems included.
In general, users can create much more complex structures with BIM than they could with 3D CAD. The complexity of some structures, like a wall system attached to columns and floor slabs could easy be created with BIM but would require a major application extension in 3D CAD.
One huge problem encountered with BIM, though, is scalability. Many problems can occur when a BIM project model is too large. Program operations can become slow and unworkable. I have had many experiences with this with Revit on my co-op and understand why this is a huge problem. One thing we did to try to keep each model more simple was create one for architecture and interiors and one for mechanical, electrical, and plumbing. For really large buildings, all major disciplines were kept in separate models. Overall, I believe that BIM is an amazing tool for the building industry and I can't wait to see the future of BIM.
Catherine Stevens looked at all current BIM programs separately and chose which system she thinks she would enjoy using the most. She believed that Bentley Systems would be the best to use because of the broad range of building modeling tools. I thought that was interesting because large companies usually use Autodesk Revit. I hope to use Bentley Systems soon to see what I think, as well.
Ilana Ritvalsky discussed how she always wondered why Revit's user experience was so different than regular AutoCAD. I also often wondered this. I knew they were very different, but after reading this chapter, I learned so much more. I now know the large differences between BIM and CAD and I am excited to be able to explain this to people who aren't believers in BIM.
J Schwakoff noticed how the chapter says that contractual processes and work culture are expected to continue to center around 3D drawings. I too am confused as to why this is. I would think that 3D drawings could greatly help during the construction process. Maybe it is just because 2D drawings are what contractors are used to and sometimes it just takes time to change.
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