Seismic performance of interior precast concrete beam-column connections with highly ductile fiber-reinforced concrete in the critical cast-in-place regions

Highly ductile fiber-reinforced concrete (HDC) is a type of fiber-reinforced cement-based composite material that is characterized by tensile strain-hardening behavior and the formation of multiple cracks. In this study, five interior precast concrete beam-column connections with HDC located in the critical cast-in-place regions, and a control connection, were tested under low-reversed cyclic loading to improve seismic performance, overcome steel congestion, address concrete compaction issues, and resolve fabrication difficulties. The failure pattern, hysteretic behavior, energy-dissipation capacity, stirrup strain, shear deformation of joint, and effect of assembly construction were all investigated. The results reveal that the application of HDC in joints significantly enhances the shear capacity and damage-tolerance capacity of joints, and changes the joint shear failure to beam end failure. However, the column should be strengthened to achieve the requirements of a "strong column" due to the application of HDC at the joint and beam end. HDC can be used to replace stirrups in confining joints to ensure good seismic performance and prevent fabrication difficulties caused by the congestion of reinforcements in joints. The 90-degree hook bottom longitudinal bar is useful for anchoring longitudinal bars in joints.