Abstract: The nonlinear behavior of structures and members must be considered in performance-based seismic design of structures. Only a small number of elements are required to get accurate results if the force-based distributed plasticity model of beam-column elements is used. It is also convenient to deal with the localization of deformation induced by the concrete strain-softening with this model. But if the element is formulated directly by numerical quadrature when solving the localization, the results will deviate from the exact solutions with the number of quadrature points increasing. To solve this abnormal phenomenon, the deformation of section is divided into elastic type and plastic type, and the length of plastic zone in the element is specified, in such a way rational results are obtained.