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

Abstract 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.

【摘要】变截面钢梁柱作为主要承重构件的应用日益广泛。准确确定其极限承载力，唯有借助有限元法（FEM）等先进数值方法方可实现。本文针对中等跨度钢框架中常用的I形截面变截面钢梁柱，系统研究了有限元（Finite Element，FE）模型参数对其极限荷载的影响。本研究旨在确定弧长法求解过程中，用于开展准确、稳健且高效的弹塑性后屈曲参数分析（PA）的最优有限元网格尺寸与子步数，同时评估各参数的影响程度。在采用八节点六面体有限单元对有限元模型完成验证后，最终选取20、25、30 mm的单元边长以及10个子步数，用于后续的参数分析。此外，本文还开展了多组有限元分析，以评估各参数的影响规律并量化其影响程度，最终得到经验公式：不含交叉项的公式误差范围为-35%至35%，含一阶交叉项的公式误差范围为-23%至23%。