Seismic response of R.C. braced frames

Abstract

This paper presents the inelastic seismic response of reinforced concrete frames with concrete bracing members arranged in X and K patterns. The braced frames had either strong, intermediate or weak bracing members whose slenderness ratio was in the order of 60, 80 or more than 120. A two-bay, six-story frame designed by limit state design procedure was subjected to the north-south component of the 1940 El Centro earthquake and an artificial earthquake. Takeda's bilinear hysteresis model was assumed for girders, and an elasto-plastic model was assumed for columns with axial force effects included. A simple triangular hysteresis model was assumed for reinforced concrete bracing members based on the test results. It accounts for different stiffnesses in tension and compression and pinching in effects. It is concluded that the inelastic seismic response of X and K braced concrete frames with intermediate bracing members is satisfactory. The behaviour of braced concrete frames is different from that of braced steel frames due to different material and hysteretic characteristics.