A unified failure criterion for concrete under multi-axial loads

A survey of existing literature shows that researchers have used different sets of failure criteria to predict the stress at failure for concrete under biaxial, triaxial and axi-symmetrical loads. Furthermore, attempts at developing a failure surface for concrete have generally been for normal strength concrete only. Therefore a new and unified 5-parameter failure surface is developed and presented in this paper. It is suitable for use with normal strength, high strength and steel fiber-reinforced concrete ranging from 20 MPa to 165 MPa. A method to modify the failure surface for plain concrete to take into account the effect of fibers in steel fiber-reinforced concrete is also presented. Comparison with experimental results shows that the proposed failure surface is suitable for the above mentioned concrete types under any load combination.