Pareto-based optimum seismic design of steel frames

Abstract

The primary objective of this work is to introduce the idea of using Pareto optimal solutions for the computation of relationships among the factors involved in seismic design of skeletal steel frames. To verify the capability of this concept, multi-objective optimisation is applied and the relations between total skeletal weight, resultant seismic base shear, maximum lateral displacement and the first eigen period of the structure are investigated. Due to the importance of structural safety and for economical reasons, due to its intrinsic conflicting nature, investigation of Pareto optimal solutions for minimisation of skeletal weight against minimisation of maximum lateral displacement of the structure is also considered. For this purpose, a fast non-dominated sorting genetic algorithm is applied to compute Pareto optimal solutions. After computing related Pareto designs, they are used to determine relationships among design factors. The design of an ordinary moment-resisting frame is considered under gravitational dead loads and seismic loads in which lateral earthquake forces are calculated from modal spectral analysis. The structures are under strength and serviceability constraints. All design requirements correspond to the uniform building code and to the allowable stress design code of practice of the American Institute of Steel Construction. The effectiveness of the proposed method is verified using some examples.