Chapter 6 - BIM for Contractors - Planning Construction

Planning construction involves sequencing activities in space and time, like the procurement of materials, labor and other concerns. This was typically represented by bar charts, and the BIM handbook claims that such a method is “unable to show how or why certain activities were linked in a given sequence; nor could they calculate the longest (critical) path to complete a project.”

Image 1: A Sample Gantt Chart

Today, we now use software such as Microsoft Project, Primavera or P3 to create comprehensive schedules (or gantt charts) which display the steps of procurement and construction, linking every task and sorting by the most critical. A specialization program, such as Vico Control, is better suited to building construction by enabling schedulers to do location-based scheduling and allow multiple teams to do repetitive work in multiple locations. Even so, only a person with sufficient familiarity with the project and with scheduling can properly evaluate a gantt chart and determine if it is a feasible schedule.

The article points to a current dilemma in which the methods we use today still do not properly capture the spatial components of building construction. It seeks to solve the shortcomings of the modern way of planning project by suggesting two solutions. The first is 4D CAD, a 3D CAD software which incorporates a construction schedule and shows the day to day process of construction in a 3D model. Faults in the design and the scheduling can be observed in space and time, which helps designers and contractors identify the issues and allow them to devise solutions. The second approach is to combine analysis tools, BIM components, and construction method information to optimize activity sequencing. This conglomerate, as the handbook explains, incorporates spatial, resource utilization, and productivity information.

Image 2: A Sample 4D software

Of the two options described in the handbook, 4D simulations seem like the most sensible. The potential for collaboration and communication between owner, designer and contractors using 4D CAD is high. Contractors can review projects to determine the feasibility and can make accurate schedules based on the design. If a community or public project uses 4D CAD, the layman will be able to understand the project may impact his day to day life. Site logistics would benefit from the use of 4D CAD since they would be able to plan laydown areas, access points and location of large equipment. Last but not least, the 4D tool can compare different schedules and can easily determine if a project is early, on track, or behind schedule.

Reference

Chuck Eastman, Paul Teicholz, Rafael Sacks, Kathleen Liston; “Bim Hanbook, a Guide to Building Information Modeling for Owners, Managers, Designers, Engineers, and Contractors” Second Edition, Chapter 5; Second Edition 2011