Seismic behavior and shear bearing capacity of Ultra-High Performance, Fiber-Reinforced Concrete (UHPFRC) beam-column joints

Abstract

This work aims to investigate the seismic behavior and shear bearing capacity of Ultra-High Performance, Fiber-Reinforced Concrete (UHPFRC) beam-column joints. Quasi-static tests were conducted on five exterior and four interior reinforced UHPFRC beam-column joints; the behavior of specimens was examined in terms of failure processes, shear deformation angle, load transfer, and loadbearing capacity. The influences of the joint types, axial compression load level, and stirrup ratio in joint cores on the failure modes and shear carrying capacity of joints were analyzed. The shear resistance mechanism of a reinforced UHPFRC beam-column joint consists of the diagonal strut and truss mechanisms. The role of steel fiber through cracks is similar to reinforcement bars in the truss mechanism; based on these mechanisms and the test results, a formula was proposed to predict the shear carrying capacity of reinforced UHPFRC joints. The formula can reflect the effects of axial compression load level, steel fiber content, and stirrup ratio in the joint core on the shear carrying capacity of the beam-column joint, which can be used not only for UHPFRC beam-column joint design, but also steel fiber high-strength concrete joints.