Experimental study on seismic behavior of cross-shaped concrete- filled steel tubular columns under diagonal cyclic loading

In order to study the seismic behavior of cross-shaped concrete-filled steel tubular (CFST) columns under diagonal loading, cyclic experiments on nine specimens were carried out. The main parameters were loading angle (0° and 45° ), concrete strength grade (C50 and C70), axial compression ratio (0, 0.25 and 0.5), presence or absence of stiffener. The hysteretic behavior such as failure mode, horizontal load-displacement hysteretic curve, skeleton curve, ductility and cumulative energy dissipation were obtained and the influences of different parameters were analyzed. A finite element model of cross-shaped CFST columns was developed. It's found that the calculated results agree well with the test results. The test results show that the cross-shaped CFST columns have good hysteretic behavior and the displacement ductility coefficients of all specimens are greater than 3.5. The axial compression ratio has great influence on the hysteretic behavior of cross-shaped columns. Increasing axial compression ratio results in decreasing load bearing capacity, faster degradation of stiffness, weaker ductility and energy dissipation. With the increase of concrete strength, the load bearing capacity increases. Under the condition of great axial compression ratio, the ductility drops dramatically due to higher concrete strength. Compared with the specimens without stiffeners, the specimens with inner stiffeners welded intermittently exhibit about 8% higher load bearing capacity, slightly better ductility and energy dissipation. The specimens at 45° loading angle show slightly superior hysteretic behavior than the specimens at 0° loading angle. © 2020, Editorial Office of Journal of Building Structures. All right reserved.