Seismic shear response of rc members with varying ductility

Experimental results of twelve reinforced concrete specimens subjected to reverse cyclic shear are presented. The tests were performed as part of a long-term research program that is presently underway at the University of British Columbia to develop a rational model for seismic shear design. The main objective of this investigation was to test reinforced concrete specimens under well-defined loading conditions in order to provide insight into the behaviour of structural members subjected to reverse cyclic shear. A secondary objective was to develop a scheme to obtain a comprehensive record of crack patterns and deformations. Enhancements made to both the experimental documentation and the specimen boundary conditions are described. A number of parameters are investigated to examine their effect on a reinforced concrete member's behaviour during reverse cyclic shear. The influence of shear span (the ratio of maximum bending moment to shear), amount of transverse reinforcement, axial load (tension and compression), and the presence of distributed longitudinal reinforcing steel are examined. It is apparent that decreasing the shear span will result in a reduction of the amount of flexural ductility exhibited by a member whereas increasing the amount of transverse reinforcement improves both crack control and flexural ductility. It is also apparent that adding axial compression increases the shear capacity of a reinforced concrete element and reduces crack angles, whereas applied axial tension results in increased crack inclinations and a reduced shear capacity. The addition of distributed reinforcing steel was found to enhance crack control and resulted in improved energy dissipation. Experimental results are compared to initial and final shear capacity predictions made using ATC-6-2 provisions. Based on the favourable agreement between the experimental and predicted shear capacities, it appears that the model successfully captures the degradation of shear strength with increased ductility demands. However, although the ATC-6-2 provisions using the simplified "Vc+Vs" method for calculating shear strength provided reasonable estimates of the initial and final shear strengths, perhaps a more refined, rational method of calculating shear resistance, such as the Modified Compression Field Theory, would improve the predictions and provide greater insight into the mechanisms present during reverse cyclic shear.Applied Science, Faculty ofCivil Engineering, Department ofGraduat