Stresses and crack angles in concrete membrane elements

This paper compares the two softened-truss models for the nonlinear analysis of reinforced concrete membrane elements: (1) the rotating-angle softened-truss model, which is simple but unable to predict the "contribution of concrete'' (V-c); and (2) the fixed-angle softened-truss model, a more complex model but capable of predicting V-c. This comparison elucidates the stresses and crack angles in a membrane element, clearly showing that V-c is caused by the shear strength of concrete and not attributable to the average tensile stress of concrete as claimed by the modified compression field theory. Two conceptual errors (one in stresses and one in crack angle) in the modified compression field theory are discussed. The correct distribution of stresses in a typical shear element is illustrated by a numerical example.