Optimal design of truss structures by logic-based branch and cut

The truss design problem is to find the optimal placement and size of struc tural bars that can support a given lend. The problem is nonlinear and, in the version addressed here, the bars must take certain discrete sizes. It i s shown that a logic-based method that dispenses with integer variables and branches directly on logical disjunctions can solve substantially larger p roblems than mixed integer programming, even though the nonlinearities disa ppear in the mixed integer model. A primary purpose of the paper is to inve stigate whether advantages of logic-based branching that have been demonstr ated elsewhere for linear problems extend to nonlinear programming.