BIM-Based 4D Modeling and Scheduling - Construction Project Scheduling and Control - page 396

Figure 15.4 Summary of functions of nD BIM
with the creation of 2D and 3D soft drawings. 3D CAD drawings can be described
as graphical entities that represent physical characteristics of the components in terms
of their length, width, and height. These drawings do not incorporate intelligent data
parameters about the project, that is, the knowledge about the physical characteristics
of the components that makes the major difference between CAD systems and BIM.
Although 3D CAD systems provide vast amount of benefits over traditional 2D CAD
drawings (i.e., the representation of how a design will perform in practice and the
visualization of architectural, structural, mechanical, and electrical drawings in 3D
environment), they fail to cover the data information (i.e., material information,
supplier information, project life-cycle information) that are assigned to individual
component objects. For example, while “an external wall” is just a wall and is described
as a three-dimensional object in 3D CAD drawings, “an external wall” in BIM means
components such as external brick leaf, internal block leaf, insulation layer, and a
protected weatherproof finish. The description of each of these objects allows the esti-
mation of quantity takeoff, activity sequencing, and automatic generation of project
schedules. Thus, to work in a BIM environment and create 4D, 5D, and nD models,
the “intelligence” of the 3D object-based models should be ensured. In summary,
while CAD systems can be regarded as 2D and 3D drawings that are created in a soft-
ware environment, BIM can be defined in terms of a database of information about a
building, a virtual platform for design, construction, maintenance, and construction,
and an automated technology for cost estimation and project scheduling.
Definition and Benefits of 3D Modeling
Three-dimensional models (3Dmodels) are digital representations of building com-
ponents and facilities in terms of spatial dimensions (width, length, and depth) as well