A restoring force model for frames with steel tube columns filled with recycled aggregate concrete

Abstract

AbstractTo establish a restoring force model for recycled aggregate concrete‐filled steel tube (RACFST) frames, the quasistatic tests on two frames comprising two RACFST columns and a reinforced recycled aggregate concrete (RRAC) beam each was carried out. The recycled coarse aggregate replacement ratio was 100%. The failure mechanism, hysteretic curves, and strain response of the specimens were discussed. By analyzing the degradation of the load bearing capacity with increasing displacement amplitude and combining the hysteretic curves and stiffness degradation relationships, a restoring force model of load versus displacement adopting a trilinear approximation was proposed. The characteristic points of the model were the relative yield point, relative peak point, and relative failure point. Results showed that bending‐shear or bending failure occurred at the ends of specimen beams and plastic hinges formed there earlier than at the column ends. The hysteretic curves of load versus displacement were essentially symmetric in a full shuttle shape. The proposed restoring force model adopting trilinear approximation agreed well with the experimental hysteretic curves under low‐cycle loading and can thus be recommended to perform the elastoplastic analysis of seismic response for this new type of composite structures.