Finite element method of strength reduction with softening constitutive model

A new iteration method with the softening constitutive model is proposed to overcome the shortcomings of the existing method of strength reduction in FEM that every computational process started from the zero stress state. In the new method, the strength reduction factor to bring slope into the limit equilibrium state after all the external loads applied was increased gradually. The method directly simulated the process of strength reduction. During the process of the yielding surface shrinking, the stresses at each Gauss' point reached the equilibrium state through stress drop and plastic flow. Two examples are given to prove the effectiveness of the method.