Shape and cross-section optimisation of a truss structure

This article presents a method for the identification of the optimum shape and cross-sections of a plane truss structure under stress and geometrical constraints. The shape design problem is defined by the unknown nodal co-ordinates and is combined with a parametric design problem defined by the cross-sections. The method includes a new approach to merge these two problems and thus resolves the difficulties that arise when combining the optimisation of variables of such different nature. The methodology combines a full stress design optimisation with a conjugates gradient optimisation. The results are compared to steel bridge constructions built at the beginning of the century, when saving material was of great importance.