Abstract
A model based on upper bound theorem was proposed to give shear failure surface of R/C columns subjected to vertical and biaxial horizontal loads. The failure mechanism assumed in the model was defined by four parameters, and the solution was obtained theoretically. The effect of axial load, direction of horizontal load, and amount of lateral and vertical reinforcement on shear strength was studied by using the proposed model. The study has revealed that: (1) there is interaction between vertical load and shear strength, (2) the shape of shear failure surface under constant vertical load is an ellipse and the direction of displacement coincides with the one normal to the surface, and (3) vertical as well as lateral reinforcement influences shear strength.
