Second-order plastic-hinge analysis of space semi-rigid steel frames

This paper presents a numerical procedure based on the beam–column method for nonlinear static analysis of space semi-rigid steel frames. The second-order effects are considered by the use of stability functions obtained from the exact solution of beam–columns under end forces and the inelastic behavior of material are presented by the lumped inelastic concept using yield surface. An independent zero-length element comprising of six translational and rotational springs, of which rotational spring stiffness uses the Kishi–Chen power model, is used to simulate the rigidity of the steel beam-to-column connection. The generalized displacement control method is applied to solve the nonlinear equilibrium equations in an incremental–iterative scheme. The nonlinear response results are compared with those of existing studies to verify the accuracy of the proposed numerical procedure.