Seismic shear behavior of partially-encased composite column to steel beam joint: Experiment

This paper aims to investigate the seismic shear behavior of the composite joint consisting of partially-encased composite (PEC) column and steel beam. Two specimens, including one PEC column (strong-axis direction) to steel beam joint and another PEC column (weak-axis direction) to steel beam joint, were tested under constant axially compressive load on the column and cyclic load at the top of column. The designs and fabrications of specimens were described in detail. The failure modes of these two type joints were obtained, their joint panel zone were all failed by shear, and several indexes that could reflect the seismic performance of the composite joint, such as the hysteretic curves, the ductility, the stiffness degradation, and the energy dissipation capacity were analyzed. It was founded that the ductility coefficients of the strong-axis joint specimen and weak-axis joint specimen are both close to 2.0, the shear failure of these joints should be avoided in seismic region. The T/CECS719-2020 shear strength models produced conservative predictions of the shear bearing capacity of these joints. The predicted shear bearing capacity of strong-axis joint is 60.12% of the experimental value, and the predicted value of weak-axis joint is only 32.46% of the experimental value. The prediction of the shear bearing capacity of weak-axis joint should consider the role of the column flanges and the concrete not wrapped by connecting plates in shear resistance.