Evaluation on Seismic Performance of Dual Steel Moment-Resisting Frame with Zipper Bracing System Compared to Chevron Bracing System against Near - Fault Earthquakes

Abstract

In order to design buildings against earthquakes, it is necessary to get comprehensive information about their behavior against the forces induced by earthquakes. According to the structural codes, the designed structures should not be damaged against light or moderate earthquakes so that the members should have sufficient strength and safety while they should be a ductile complex with a proper structural configuration against sever earthquakes to dissipate the forces caused by ground motions. In the design of steel buildings, use of moment-resisting frames in combination with braces is a seismic-resistant system. One of these system is the dual steel moment-resisting frames with zipper braces. In this research, the seismic performance of the moment-resisting frame with zipper brace system has been studied and its performance has been compared to the performance when the chevron bracing system is used. Three 4-story, 8-story and 12-story buildings have been selected as representatives for low-rise, mid-rise and high-rise buildings, respectively and then they have been modeled by SAP2000 software and finally, their seismic performances have been evaluated using time history analysis. The structural responses have been compared as comparing the relative displacement of the stories (story drift), the maximum displacement of roof, and the formation of plastic hinges in the members. The results of current study show that using a zipper member decreases both overall displacement of the structure and the damage index so that it directs formation of plastic hinges from horizontal and vertical members toward diagonal members.

Keywords

• dual steel moment-resisting frame
• zipper brace
• chevron bracing system
• history analysis
• sap2000