Collapse of I-section tapered beam-columns in medium-span steel frames: Finite element model validation and parameters influence evaluation

Tapered steel beams and columns have been increasingly used as primary load carrying members. The determination of their accurate ultimate capacity can only be achieved employing advanced numerical methods such as the finite element method (FEM). This paper presents a systematic study on the influence of FE model parameters on the ultimate load of I-section tapered beam-columns typically used in medium-span steel frames. It aims the determination of optimal FE mesh size and sub-step number to be used during the arc-length scheme for the performance of an accurate, robust and efficient inelastic post-buckling parametric analysis (PA) as well as the evaluation of the parameters influence. Once validated the FE model, using hexahedral 8-node finite elements, FE edge sizes of 20, 25 and 30 mm and 10 sub-steps have been selected for use in the future PA. Several FE analyses were also carried out to evaluate how it is and quantify the influence of each of the parameters, leading to empirical equations with errors in the range of -35% to 35% for equations without crossed terms and -23% to 23% with first-order crossed terms.