Stress-Strain Model for Confined Reinforced Concrete in Bridge Piers

In this paper, a stress-strain model of concrete that takes confinement effects into account is developed, based on the results of a series of compression loading tests of reinforced concrete column specimens. The specimens have circular, square, and wall-type cross sections, with various arrangements of hoop reinforcement so as to cover practical bridge column sections designed in Japan. Test results showed that three parameters—peak stress, strain at peak stress, and deteriorating rate—are significant factors for the stress-strain curve of confined concrete. These parameters were analyzed statistically based on test data and equations for estimating them were proposed. An equivalent confined section was also proposed to evaluate effect of cross ties in wall-type cross section. Test results were compared with both the proposed model and existing models. The comparison showed that the predicted stress-strain relation by the proposed model provides better agreement with the experimental results than existing models.