Discrete optimum structural design

Abstract

This paper is concerned with some of the difficulties involved in the optimum design of engineering structures using only components which are available in discrete sizes. As an example the optimum design of trusses using rolled steel sections is used to critically examine several different methods and point out the snags in using them in a computer-aided design context. The combinatorial nature of the problem is described and heuristic methods for finding non-rigorous but very close discrete optimum designs are discussed. An investigation of the practical needs of structural designers rather than the capabilities of numerical algorithms demonstrates that the nature of the discrete design problem is in practice very different from that perceived by many researchers. The paper then examines possible ways of solving the practical optimum design problem rather than the problems most often tackled in the literature.