Seismic performance of a ring beam joint connecting FTCES column and RC / ESRC beam with NSC

Fiber-reinforced polymer (FRP) tube-concrete-encased steel (FTCES) composite column shows superior load-bearing capacity, stiffness, deformation capacity and it has excellent corrosion resistance. However, its practical application is very limited due to few experimental and analytical studies on the behaviour of the entire structural system. Indeed, the most challenging part in the structural system is the beam-column joint, which should be carefully designed since it may govern the reliability and stability of the structural system when suffering seismic attack. To fill up this research gap, this paper investigated the seismic performance of a ring beam joint connecting FTCES column and reinforced concrete (RC)/encased steel RC (ESRC) frame beam casted with normal-strength concrete (NSC). A total of four beam-column joints were designed and the effect of ring beam reinforcement ratio, axial force ratio and frame beam type on the seismic behaviour of the joints was studied. Results showed that the proposed joint could provide reliable connection and exhibited favorable seismic performance. Besides, the failure occurred at the location of ring beam, frame beam or the connection between ring beam and frame beam. In addition, the effect of ring beam reinforcement ratio and axial force ratio on the hysteresis curve, skeleton curve, peak load, ductility and (accumulative) dissipated energy was insignificant while the ESRC frame beam could effectively enhance the seismic behaviour of the joint. In the meanwhile, the ESRC frame beam could effectively mitigate the strength and the secant stiffness degradation. •Four ring beam joints connecting FTCES columns and RC/ESRC frame beams were prepared.•Effect of ring beam reinforcement ratio, axial force ratio and beam type on the seismic behaviour of the joint were studied.•ESRC frame beam could effectively enhance the seismic behaviour of the joint.