ANALYSIS ON AXIAL COMPRESSION BEHAVIOR OF PENTAGONAL CFST MEGA COLUMNS

Based on the pentagonal concrete filled steel tubular (CFST) mega columns of a super high-rise building, axial compressive behavior of pentagonal CFST mega columns with different cross-sections and detailing were studied. Monotonic cyclic loading tests of 3 pentagonal CFST mega column specimens were conducted under axial compression. 3 specimens were respectively: a single-caved section with a reinforcement cage, a quadruple-caved section without reinforcement cage and a quadruple-caved section with reinforcement cages. Axial force-deformation curves were obtained. The failure mechanisms, residual deformation and elastic-plastic energy dissipation capacities were analyzed. Methods for calculating the ultimate bearing capacity of CFST mega columns were proposed. Finite element simulations are carried out based on ABAQUS for analyzing the effects of cross-sectional and detailing parameters, including the number of cavities and the presence of reinforcement cages on member behavior. The simulation results agree well with the test results. It is concluded that quadruple-caved sections have greatly increased the bearing capacity and ductility with less residual deformation and better energy dissipation capacity compared with single-caved sections. Additionally, quadruple-caved sections with reinforcement cages have further increased the bearing capacity, ductility, and the energy dissipation capacity with even less residual deformation compared with quadruple-caved sections without reinforcement cages. Pentagonal CFST mega columns with quadruple-caved sections and reinforcement cages have comprehensively good compressive behavior, which can be used in the design of super high-rise buildings.