Design optimization of structural steelwork using a genetic algorithm, FEMand a system of design rules

In this paper a structural optimization technique based on a modified genet ic algorithm IGA) is presented The technique is developed to deal with disc rete design optimization of structural steelwork Also, the paper discusses the effect of different approaches, employed for the determination of the e ffective buckling length of a column, on the optimum design. In order to co nsider realistic steelwork design problems, a modified GA has been linked t o a system of structural design rules (;(British Standards BS 5950 and BS 6 399), interacting with a finite element package. In the formulation of the optimization problem, the objective function is the total weight of the str uctural members, as it gives a reasonably accurate estimation of the cost. The cross-sectional properties of the structural members, which form the se t of design variables, are chosen from two separate catalogues (universal b eams and columns) covered by the British Standard BS 4. The minimum weight designs of two plane steel frame structures subjected to realistic multiple loading cases are obtained. These examples show that the modified GA in co mbination with structural design rules and more accurate analysis provides an efficient tool for practicing designers of steel frame structures. Final ly, it is shown that the resulting design optimization is considerably infl uenced by a specific choice of a technique employed for the evaluation of t he effective buckling length of structural members.