Group A: BIM vs. Drafting (Advantages and Disadvantages)

BIM is a system through which a 3D model can be used to produce both 3D and 2D drawings. In addition to drawing, BIM is based on databases from which information on the type of object being drawn can be extracted. This database can also be used to come up with schedules.

One of the advantages of BIM modelling, I learnt more about last week. This is parametric modeling. BIM systems have the ability to change a portion of the structure and other parts of the model will change in accordance. For example, if the size of a wall has to change, the slab thickness and sizes of the other walls will change to accommodate for the new wall dimensions. CAD programs such as Autocad do not have this ability. The designer, after changing the dimensions of one wall, would have to go through all the objects that are affected by this change and alter them accordingly.

Figure 1 shows that that with BIM programs, most of the work is concentrated in the design process while with CAD drafting, when changes had to be made, since it takes longer to make these changes, the most amount of work would be concentrated in the construction documentation phase of the project. “Civil engineers typically design for code compliance, not for constructability. But incorrect interpretations about design intent made in the field because of ambiguous documentation can lead to delayed schedules, change orders, and RFIs after construction begins.” [2]

Another advantage of BIM programs is that through the database, a designer is able to determine how many cubic feet of concrete are being used for the walls. This is not something that was previously available in CAD programs.

BIM has become so well known that even clients have begun to understand its effect on the design process. As a result, clients know that changes can easily be made. Making changes late in the process can lead on an increase in design and construction costs.

Another disadvantage is that a large amount of file space is required. This means that there has to be a change in the computer hardware as a result of the change in the software.

Comments
Mike: It was interesting reading about how BIM will actually improve buildings not just improving the ease of their design. I had not thought about how this would change especially for the HVAC system; improving the thermal comfort of occupants. I don't know Revit that well but I believe it is able to determine how energy efficient a room is and takes into consideration not just the HVAC system but other ways in which heat/energy can be released and absorbed. BIM will help reduce the amount of energy that is wasted in the building.

Steve: You're definitely right in saying that BIM will lead engineers to be more creative with their models due to the reduction in the amount of time spent making changes. As Mike also discussed, HVAC is a component of the model that may be most affected due to the improvement in the estimation of the energy efficiency of the room. I find the urban planning option really interesting since it would be helpful with my senior design project.

Matt: I found it interesting that you talked about how engineers have a hard time adapting to Revit. I believe this is one of the fears of companies that inhibit them to switch over. However, the ability of BIM to coordinate between different disciplines hugely outweighs how long it would take for engineers to get used to the program. 

References

1. Lister, David. "What Is BIM?" Precise Drafting, Inc. N.p., n.d. Web. <http://www.precisedraftinginc.com/bim.html>.

2. Strafaci, Adam. "What Does BIM Mean for Civil Engineers?" CE News. ZweigWhite, n.d. Web. <http://www.cenews.com/magazine-article----what_does_bim_mean_for_civil_engineers_-6098.html>.