Considerations on Advanced Analysis of Steel Portal Frames

This paper presents a little study about the necessary steps to qualify a second- order inelastic analysis as advanced one. Plastic-zone approach is applied to steel plane frames (portals) and the numerical formulation is based on finite element model of a Bernoulli-Euler beam-column member using the called “slice technique”. This element is set on a Lagrangian updated co-rotational system. The nonlinear problem is solved using Newton-Raphson iterative strategy and a new axial force iterative integration is shown. This process was implemented on a computer program PPLANAV* and the minimum requirements of advanced analysis (initial geometrical imperfections and residual stress) are automatically generated. Two examples show good agreement with other researcher’s answers, but there’s a great elapsed computing time.