Deteriorated Hysteresis Behaviors of Reinforced Concrete Bridge Columns

Five rectangular tie-reinforced bridge columns were tested in this study to investigate the effects of longitudinal reinforcement ratio, aspect ratio, and confining mechanism on their deteriorated hysteresis behaviors. Results were compared with another five spiral-reinforced circular bridge columns reported in the litera-ture; the identified deterioration characteristics of columns indi-cated that the stiffness degradation and pinching effect of a column would increase as its longitudinal reinforcement ratio decreased. In contrast, the aspect ratio of a column had negligible influence on its stiffness degradation, but its pinching effect increased as the aspect ratio decreased. Due to the better confining mechanism, the severity of deterioration in circular columns was lower than in rectangular columns. The failure in rectangular columns was initi-ated by the hook loosening of closed hoops and crossties, resulting in gradual strength deterioration, while the failure in circular columns was triggered by the fracture of spirals, resulting in signif-icant strength drops.