Optimization of Long-Span Cold-Formed Truss Purlins

The value of mathematical optimization tools for the cold-formed steel industry is investigated by using a particular technique to redesign a building systems product already being successfully marketed. The optimization technique employed is a variation of the cutting-plane method wherein a sequence of linear programming problems is solved to obtain the solution of the nonlinear problem. Twenty-four design parameters and 64 constraints, mostly nonlinear and drawn unchanged from the Specification for the Design of Cold-Formed Steel Structural Members (AISI), form the nonlinear programming problem that is solved for the design. Most of the constraints involve buckling behavior of some form. An example using a member of the class of components that was redesigned is employed to demonstrate how the problem is set up for solution.