Nonlinear Inelastic Analysis for Steel Frames

The manuscript shows a second-order inelastic analysis procedure for steel framed structures under static and seismic forces. Nonlinear inelastic finite element formulations are established utilized Stability Functions (SF) solved from exact solutions of second-order differential equations of beam-column finite element subjected to moments and axial forces. Stability functions help optimize modeling and computational time because only one element per member is used for beams or columns. Plasticity of steel can be modeled by two approaches: the plastic hinge (PH) and plastic fiber (PF). Generalized Displacement Control (GDC) algorithm is adopted for solving equilibrium equations for static problems, while the Newmark method and Newton-Raphson iterative algorithm are adopted aim for solving dynamic equilibrium equations. A verification example is shown to prove the computational efficiency, accuracy, and prove the convenience of the program for engineering analysis and design.