A method for coupling the variable damage to the yield function of a 2D beam element is presented. The damage is represented by a scalar internal variable which expresses the loss of strength of the material during ductile or fatigue processes and it is concentrated at the ends of the element. Yield surfaces, considering the interaction of bending moment, axial force, shear force and damage of material are also given. And the yield function obtained can be used to determine the elastoplastic stiffness matrix of beam element used for the structural analysis.