Cyclic behaviors of reinforced concrete beam-column joints with debonded reinforcements and beam failure: experiment and analysis

It was experimentally validated that partially debonded high-strength longitudinal reinforcement can provide strong self-centering capacity to minimize residual deformation, and greatly mitigate seismic damage of column. To continuously investigate the influence of partially debonded longitudinal rebars (PDLR) of column and beam on seismic behaviors of beam-column joint assembly, three interior and three exterior joint specimens were fabricated to subject to cyclic lateral loading. It was showed experimentally that joint specimens with PDLRs in both beams and columns had slighter seismic damages, smaller stiffness and energy dissipating ratios, better ductility compared with joint specimens without PDLRs in the beams. Furthermore, the lateral load of joint specimens without PDLRs in the beams decreased from lateral drift of about 4.0%-5.0% due to much crushing and spalling of concrete in the compressive zones of the beams. Whereas, joint specimens with PDLRs in the beams had continuously increased lateral load until lateral drift up of 10.0%. An analytical approach was derived to evaluate the lateral behavior of beam-column joint assembly which can considering joint deformation and steel bond slip. The proposed approach can reasonably predict the lateral behaviors of joint specimens with or without PDLRs. Analytical results indicate that approximately 70% of total deformation of joint specimens with PDLRs in both beams and columns is contributed by slippage deformation of the beams, whereas, that contribution ratio of the other joint assembly specimens is only 30%.