Pseudostatic testing for load-carrying capacity of precast concrete-encased steel composite columns

Abstract

To combine the advantages of concrete-encased steel columns, high-performance concrete and precast structures, an innovative steel composite column encased in precast high-performance concrete is proposed in this paper. The proposed composite column is composed of a precast outer part and a cast in situ inner part. The precast part can be prefabricated using steel-fiber-reinforced reactive powder concrete (RPC), and the inner part can be cast using conventional concrete. With an aim of exploring seismic behavior of this innovative composite column, three of them were designed and subjected to constant axial compression and cyclic loading, with the main test parameter being the shear span-to-depth aspect ratio. The failure mode, hysteresis loop, skeleton curve, lateral stiffness degradation, energy dissipation and displacement ductility ratio were all analyzed to investigate the effect of aspect ratio on cyclic behavior. Test results indicated that no apparent concrete spalling was found in any of the specimens, due to application of steel fibers in RPC, and the structural steel, precast outer-shell and cast in situ inner part behaved compatibly without any visible slippage. Meanwhile, initial stiffness and load-carrying capacity of the test specimens increased with a decrease in aspect ratio, and energy dissipation and displacement ductility increased with the increasing aspect ratio. Based on the test results, two calculation methods (per AISC 360–10 and JGJ 138–2016) were put forward to predict the load-carrying capacity of the test specimens. The model based on AISC 360–10 overestimated the load-carrying capacities of test specimens, while the model based on JGJ 138–2016 predicted capacities that agreed well with the test results.