Preliminary design

How do we define the main structural members so that other design teams can proceed with detailed plans?

Every project relies on preliminary design. During this stage, the structural team traces the load path and determines member sizes. Architectural, mechanical, and electrical teams solidify their decisions after preliminary design. Construction and finance teams decide how to complete the project. Each team needs the structural team’s preliminary design work.

Our exercise is to design a roof beam. We approach this exercise during the preliminary design stage. Figure 1 illustrates the sequence of our method.

Let’s assume that we have a site location and drawings supplied by the architect. Figure 2 presents the relevant portion of the drawings required for our exercise. We will design Beam RB-3, an exterior roof beam in a three-storey office building. Some simplifications are necessary so that we may focus on our exercise — determine the trial beam sizes and evaluate aspects of the design.