Determination of the load – displacement curve of moment resisting steel frames under horizontal loading

Abstract

 Seismic resistant steel frames are very common in regions of high seismic risk due to their excellent characteristics in terms of strength and ductility. For the evaluation of the total ductility, various methods have been proposed in the bibliography. In this paper a method is proposed for the evaluation of the total ductility in steel structures, which takes into account the exact form of the moment–rotation curve, including possible softening branches. In the above method, the strength degradation due to second order phenomena is also taken into account. The numerical algorithm presented in the paper is based on the background of nonconvex optimization theory. Numerical examples demonstrate the potential of the proposed method.