A post-tensioned hybrid beam-column connection with a web friction device: Experimental study and theoretical analysis

An innovative post-tensioned hybrid beam-column connection with a web friction device (PTH-WFD) was proposed to mitigate concrete crushing of precast members and to avoid the onsite aerial tension of steel strands in reinforced concrete (RC) structural systems. The proposed PTH-WFD connection was assembled using a precast hybrid (PH) beam and a precast RC column with high-strength bolts. The PH beam consisted of an RC beam and two short steel arms on both sides, and post-tensioned (PT) steel strands and WFDs were employed in the PH beam to provide a self-centering capacity and an energy dissipation capacity, respectively. To explore the seismic behavior of the proposed connection, cyclic tests were conducted on five specimens to evaluate the seismic behavior of the proposed connection, and the effects of the initial PT force on the steel strands and the clamping force in the WFDs were investigated. During the test process, few cracks were observed on the primary structural components, namely the RC beam and column, and the damage was primarily concentrated on the steel arms. The test results indicated that the proposed connection could exhibit a typical two-stage hysteretic behavior, namely, a self-centering stage and an energy consumption stage. In the first stage, the contact interface between the steel arms and the RC beams presented a continuous opening-to-closing mechanism when the drift ratio was less than 1.5%, indicating that the residual deformation was controllable and that a self-centering behavior could be achieved. In the second stage, the short steel arms yielded when the drift ratio was larger than 1.5%, indicating that the residual deformation increased and the energy dissipation significantly increased. In addition, the peak load and displacement ductility ratio increased with an increasing clamping force in the WFDs, and the peak load also increased with an increasing initial PT force. Based on the test results, a theoretical moment-rotation model was proposed, and the calculated results were in good agreement with the test results.