Cyclic shear behavior of concrete columns with debonded and low-bond high-strength rebars

Abstract

To investigate the shear strength behavior of concrete columns with longitudinal rebars under different bond strength conditions, a total of 13 test columns were fabricated using debonded high-strength PSB 830 rebars and low-bond high-strength SBPDN 1275/1420 rebars. These columns were subjected to both cyclic lateral and compressive loading. The experimental results indicated that shear damage decreased with increasing debonding length and decreasing bond strength of the longitudinal rebars. Notably, the maximum reduction in lateral resistance was approximately 11.8% when the debonding length equaled the sectional height. However, the lateral drifts at peak lateral forces were similar across all test columns. Interestingly, the transverse reinforcement strains in columns with debonded PSB rebars did not reach the yield point. The contribution of shear deformation to total lateral displacement decreased significantly—from approximately 80% to 20%—as the debonding length increased from 0 to 800 mm. A similar trend was observed in columns reinforced with longitudinal rebars of varying bond strength. Based on the experimental data, equations were developed to predict the nominal shear strength, degraded drift, and post-shear stiffness. Comparisons between the predicted and measured results showed that the proposed models accurately captured the shear strength and failure modes of columns with debonded and low-bond rebars. This study provides fundamental insights for designing safer and more resilient concrete structures using debonded and low-bond high-strength rebars.