A NONCONVEX OPTIMIZATION APPROACH FOR THE DETERMINATION OF THE CAPACITY CURVE AND THE PERFORMANCE POINT OF MR STEEL FRAMES EXHIBITING SOFTENING UNDER SEISMIC LOADING

摘要

In this paper, a new numerical method has been proposed which allows the investigation of the influence of the softening branch of the moment-rotation law to the seismic behaviour of steel frames. From the numerical examples treated here it was concluded that the softening branch plays a secondary role to the overall seismic behaviour of the structure. Due to the greater plastic rotations that result in the case of the softening law, the modeling of the softening branch is very important because the increased rotations that correspond to the softening law might be beyond the acceptability limits required by the performance objective. This is also an important difference between displacement based design and force based design.