Multiobjective Optimization for Life Cycle Cost Oriented Seismic Design of Steel Moment Frame Structures

Abstract

Life cycle cost oriented seismic design of steel moment resisting frame structures is formulated as a multiobjective optimization proble m that treats initial mat erial/construction cost, lifetime seismic damage cost, and the number of different sta ndard steel section types as three separate objective functions. The static pushover analysis is used for estimating seismic structural performan ce in terms of maximum interstory drift ratio demands. In accordance with SAC/FEMA guidelines, the seismic damage cost is computed with percentile probabilities of a spectrum of damage states that are demarcated by respective interstory drift ratio capacit ies. A multiobjective genetic algorithm is selected for the posed optimal design optimization problem. The present procedure naturally integrates user -specified confidence level on damage cost estimate and produces a wide distribution of alternative design s that exhibits an optimized tradeoff among relevant conflicting objective functions. Therefore, designers have much freedom to determine the final structural design with a preferred balance of initial coat and damage cost , while taking into due account th e design complexity