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

Abstract

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 lowcycle 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.composite column, finite element method, hysteresis curve, reactive powder concrete, restoring force model, square steel tube | INTRODUCTIONConcrete filled steel tubular (CFST) columns are superior in bearing capacity, toughness, constructibility, fire resistance, and cost effectiveness. As a result, CFST columns have been widely used in industrial plants, bridges, and buildings. However, with the vigorous development of high-rise buildings, higher performance of CFST columns is required in component size, bearing capacity, and lateral stiffness. In addition to increasing the steel content and improving the section configurations, reactive powder concrete (RPC) can be filled internally to meet these requirements. Compared to high-strength concrete (HSC), RPC has excellent mechanical properties such as higher strength, toughness, and durability. [1,2] Its compressive strength is two to four times, fracture energy is 200 times, and the chloride ion permeability coefficient is 1/60 of HSC. However, the disadvantages of RPC, such as its brittleness and poor ductility, limit its development in the engineering field. The compressive strength and deformation performance of RPC can be significantly improved with the confinement of steel tubes. Therefore, the combination of steel tubes and RPC has great advantages.CFST structures include composite structures of different steel tubes and different types of concrete. The seismic performance of CFST structures was studied with different concrete strength, steel strength, restraint coefficient, axial compression ratio, and diameter-to-thickness ratio as parameters. [3][4][5][6] Fam et al. [7] and Ge and Usami [8] studied the seismic performance of CFST specimens under the combined action of axial compression and lateral cyclic loading and concluded that CFST has high strength and good duct...