An ecient computational procedure for collapse analysis of framed structures is described. The procedure makes use of co-rotating nonlinear beam±column elements, connected at nodes, that may develop plastic hinges. The formulation incorporates a series of novel features that greatly enhance the eciency of the computations. The secant and tangent stiness of the beam±column element are obtained from a six-component equilibrium format in explicit form as a nonlinear function of the normal force, and initial imperfections and shear ¯exibility are incorporated into the explicit format. The yield functions used in the plastic hinges are extended to the full generalized stress space in a form that optimizes the convergence rate of the iterative return algorithm, and the eective length of the plastic hinge is assessed from the moment distribution in the element. The equilibrium format of the beam±column element enables a simple explicit modi®cation of the theoretical elasto-plastic tangent stiness to obtain the corresponding algorithmic stiness that accounts for the ®nite stress increments of the numerical algorithm. These features have been implemented into a ®nite element collapse analysis program RONJA, and two realistic oshore analysis examples are included to illustrate the performance of the computational procedure.