Shear capacity estimation of core steel tube reinforced PCCC column-beam interior joint under quasi-static load

Abstract

In this study, the quasi-static tests were conducted on 13 core steel tube (CST) reinforced PVC-CFRP confined concrete (PCCC) column-beam interior joints. Distinct shear failure occurred in all joint specimens. The load-displacement hysteresis curves appeared pinching phenomenon, and the shape of hysteresis loops gradually deformed from shuttle to arch and finally changed to reverse S shape. The overall shape of hysteresis curves were relatively full, demonstrating that the joints had favorable seismic performances and energy dissipation capacity. The strain development law of materials in the joint area in the process of stress was clarified. The increment of joint stirrup ratio ( ${\rho }_{\mathrm{s}\mathrm{j}}$ ), axial compression ratio ( $n$ ), column reinforcement ratio ( ${\rho }_{\mathrm{c}}$ ) or beam reinforcement ratio ( ${\rho }_{\mathrm{b}}$ ) improved the calculated shear capacity of the joints. The calculated shear capacity increased first and then decreased slightly as the diameter-thickness ratio of CST ( ${d_{\mathrm{s}}/t}_{\mathrm{s}}$ ) increased. In comparison, spacing of CFRP strip had little impact on the calculated shear capacity. Additionally, the concrete strength enhancement coefficient ( ${\eta }_{\mathrm{j}\mathrm{c}}$ ) and joint stirrup utilization coefficient ( ${\psi }_{\mathrm{s}\mathrm{j}}$ ) were introduced respectively to modify the shear capacity of concrete and joint stirrups, and a simplified formula for predicting the shear capacity of CST reinforced PCCC column-beam interior joints under quasi-static load was proposed. The predicted results agreed well with the test data.