Restoring force model of square tubular columns filled with extra‐high‐performance reactive powder concrete

Summary Square tubular column filled with extra‐high‐performance reactive powder concrete (RPC) is a novel composite structure that takes advantage of strong bending resistance of steel tubes and high compressive strength and toughness of RPC. To study the seismic performance of square tubular columns filled with RPC, a series of low‐cycle lateral loading tests were performed on four square tubular columns filled with RPC. The steel content and steel fiber content were selected as test parameters. Experimental results show that a higher steel content and 1% steel fiber result in good energy dissipation and deformation performance of specimens. To establish the restoring force model of square tubular columns filled with RPC, 18 column models with different steel content, axial compression ratio, and slenderness ratio were simulated and analyzed using ABAQUS. The simulation results show that a larger steel content and smaller slenderness ratio can improve the column bearing capacity, but the influence of axial compression ratio is negligible. A restoring force model considering stiffness degradation is proposed using a regression analysis method, which is in good agreement with the experimental results.