Numerical study of arch shaped corner brace segments in simple steel frames to provide seismic resisting system

Typical braced frames, in comparison with rigid frames, have higher stiffness but they have low ductility. On the other hand, rigid frames have high ductility but due to their low lateral stiffness, they maintain large displacements throughout earthquake, which is not favorable. Furthermore, in rigid frames, the beam to column connection is a critical area that often experiences damage during earthquake. In this research, the objective is to create a lateral load-carrying system and improve the seismic performance of steel frames using placement of arch segments cut of steel plates at the corner of simple steel frames and their yielding. Due to the eccentricity, these components are subjected to an interaction of axial and flexural forces and like yeielding dampers absorb the major part of the input energy. In this study, first, hysteresis curve of arch segments made by ST37 steel was achieved using finite element software, ABAQUS. Then this damper was modeled in SAP software to create the same hysteresis curve. Then, 3, 6 and 9-story bare rigid frames and simple frames with arch segments were modeled and subjected to time-history analysis of 12 different earthquakes. Based on achieved results, maximum roof displacement and maximum story drifts of frames, in simple frames with arch segments compared to bare rigid frames in average reduced 22 and 8%, respectively. Also in simple frames with arch segments in average 46% of input energy was absorbed by arch segments that indicates relatively good performance of this system.