A beam model for nonlinear static and dynamic analysis of seismic r/c frames is presented, which is composed by subelements connected in series. One describes the inelastic behavior of the member with gradual spread of plastic regions at the member ends. Other models the fixed-end rotation that arises at the beam-joint interface. A special form of the Newton-Raphson method is implemented to solve the nonlinear problem. Two examples for validation are shown. In the first the results are compared with other beam element and bidimensional finite elements, and in the second example the importance of the fixed-end rotation is evaluated, and the results are checked from experimental information.