B2: Group A - Samuel Boyce

This chapter aims to look at the difference between Building Information Model (BIM) and Computer Aid Drafting (CAD) software. BIM software evolved from CAD as certain industries, particularly the aerospace industry, saw improvements that could be made that they would stand to benefit from. The key development is the addition of parametric modelling. Not only does this allow 3D models to be created, it also allows the addition of non-spatial data.

Firstly I would like to discuss how the parametric modelling has influenced the ability to create 3D models. Modern BIM software comes with preloaded items that can be utilized, but users are also allowed to create their own units, and along with it the appropriate data. In terms of spatial data, typically the entered data is a definition of the shape, its own local coordinates, and its global coordinates. The local coordinates define the size of the shape, but the real importance lies in the global coordinates. These global coordinates locate the shape with regards to everything else in the drawing. It is these global coordinates where BIM really comes into its own. By utilizing these, local changes in turn have a global impact. A great example is shown in Chapter 2 where a change made to the skin of the façade results in the panels and skeleton shifting in relation to this. This ability is in stark contrast to 2D CAD programs, where there is connectivity between objects and changes on a global scale must be propagated manually.

Another part of BIM that this chapter covers, and one that I would like to draw special attention to, is the inclusion of non-spatial data. This data can range from simple financial figures to mechanical data. I would again like to emphasis that this data can be used on a global scale. For example the financial data can be tallied in order to get cost figures for the model. This ability was being utilized at my last co-op with the construction of their new building. The entire building was being modelled in BIM, and this included all of the systems. There were many reasons for doing this. Firstly there is the simple ability to just view where everything is in relation to other components. In their older buildings, ceiling tiles would have to be removed and walls surveyed in order to know exactly where systems were. Now it is simple as opening a computer file and the entire building can be manipulated and decisions made at a lesser cost. Another reason for doing this is to help maintenance staff. This plays off the first reason. A maintenance worker can enter this program and select a system, and the parametric data entered for that system would populate the screen. This includes Operations and Maintenance manuals. This means work can be planned out before setting foot in the building. Training can also be carried out using this system. Finally, as mentioned before, the global parametric data allows tallies of the financial data, water, electric, and gas capacity to be easily visualized.

Reference

Eastman, C. M. (2011). BIM Handbook : A Guide to Building Information Modeling for Owners, Managers, Designers, Engineers and Contractors. Hoboken, NJ: Wiley.


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