Influence of bond property of longitudinal bars on seismic behaviour of reinforced-concrete columns

Abstract

Four circular fly-ash concrete columns reinforced by steel rebars with different bond levels were tested to investigate the influence of bond strength of longitudinal steel rebar on the seismic behaviours of reinforced-concrete (RC) members. Furthermore, a fibre-element method considering steel bond slip was used to investigate the influence of bond properties of steel rebar on seismic responses of circular RC columns, with the test results used to validate reasonability. The comparison of results shows that the anchorage of the steel rebar has a significant influence on, and the plastic hinge length no effect on, the seismic behaviours of the columns. The analytical and test results show that low bond strength delays the yielding process of steel rebars adjacent to the beam–column interface, which can improve the deformability of RC columns, but does not obviously influence the moment resistance. However, the stiffness of the cross-section is reduced from a certain drift level. Six equations are proposed to predict with very good accuracy the reduced ratio of the stiffness of the cross-section, the enhanced ratios of the drift at the ultimate moment and the drift at the maximum lateral load of the column models reinforced by bonded or unbonded steel rebars.

Seismic fragility and post-earthquake reparability of concrete frame with low-bond high-strength reinforced concrete column

“…The authors have theoretically analysed the influence of the bond strength of longitudinal reinforcement on the seismic behaviours of RC columns. The results indicated that a decrease in the bond strength can substantially improve the ductility of RC columns and that the yield process can be delayed such that the longitudinal reinforcement can be maintained in the elastic region (Wang and Sun 2020a;Wang and Sun 2020b). Based on the above theoretical foundation, the authors proposed the use of lowbond high-strength reinforcement (LBHSR) as the tensile longitudinal rebar of RC columns.…”

Seismic fragility and post-earthquake reparability of concrete encased-and-filled steel tubular bridges columns with debonded high-strength reinforcements

“…An alternative to developing SC-RC column using a simple and low-cost technology is worthy of attention. Wang and Sun [11] theoretically analyzed the seismic behaviors of RC columns reinforced by steel rebars with different bond strengths and found that a decrease in the bond strength of the longitudinal rebar delayed the yielding process, such that longitudinal reinforcement within the elastic region can provide a more durable SC force to the entire RC column. Wang et al [12,13] found experimentally that the seismic damage was slighter and the residual deformation was smaller when the RC columns were reinforced by a debonded high-strength rebar (DHSR) and a low-bond high-strength rebar (LBHSR), compared to RC columns with normal steel rebars.…”