Performance-based plastic design method For steel concentric braced frames

This paper presents a performance-based plastic design (PBPD) methodology for the design of steel concentric braced frames (CBF). The design base shear is obtained based on energy-work balance equation using pre-selected target drift and yield mechanism. In order to achieve the intended yield mechanism and behavior, plastic design is performed todetail the frame members. Three low-to-medium rise CBF (3-story, 6-story and 9-story) were designed by the proposedmethodology and current seismic codes that include provisions to design ductile concentric braced frames called specialconcentric braced frames (SCBF). Results of inelastic dynamic analyses carried out on example frames designed by thePBPD method showed that the frames met all the intended performance objectives in terms of yield mechanisms and target drift levels. On the other hand, when designed by current code as SCBF the same structures showed very poor response due to premature brace fractures leading to unacceptably large drifts and instability. Finally it should be noted that no iterations were carried out to achieve the performance objectives of CBF in the PBPD method.