Experimental study on internal precast beam–column ultra-high-performance concrete connection and shear capacity of its joint

Abstract

Precast reinforced concrete structures are increasingly being studied and adopted for their potential advantages. In this study, we tested five precast beam–column connections whose regular shape beams and columns were connected with lap-spliced steel bars in ultra-high-performance concrete (UHPC). A monolithic beam–column connection as a control specimen was also tested under reverse cyclic loading. The results showed that the application of lap-spliced steel bars in UHPC is feasible for connecting the beam and column in the joint. It is recommended that the minimum straight bar lap length in UHPC can be determined as 15db (db is the bar diameter), and the minimum hooked bar lap length was determined as 11db (with a straight extension length of 8db, inside bend diameter of 4db, and tail extension length of 5db). UHPC significantly enhanced the shear capacity of the joint owing to its high shear strength. The increases in the fiber volume fraction and stirrup volume ratio enhanced the damage-resistance property of the joint, which is beneficial for the development of beam-end plastic hinges. Therefore, the ductility of the beam–column connection can be further increased. The increase in axial load enhanced the shear capacity. To design a “strong joint,” a theoretical strut-and-tie model was proposed based on Mohr–Coulomb theory applied to the joint core to accurately calculate the UHPC joint shear capacity.