Second-order effects in locally and/or distortionally buckled frames and design based on beam element analysis

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• 作者：Xi Zhang ; ^{xi.zhang@sydney.edu.au" class="auth_mail" title="E-mail the corresponding author} ; Kim J.R. Rasmussen ^{kim.rasmussen@sydney.edu.au" class="auth_mail" title="E-mail the corresponding author} ; Hao Zhang ^{hao.zhang@sydney.edu.au" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Steel portal frames ; Structural design ; Local and distortional buckling ; Beam-element-based analysis ; Reduced tangent rigidity
• 刊名：Journal of Constructional Steel Research
• 出版年：2016
• 出版时间：July 2016
• 年：2016
• 卷：122
• 期：Complete
• 页码：57-69
• 全文大小：744 K

文摘

In the design of steel portal frames, second order effects are usually accounted for by using a second order elastic analysis to calculate the deformations and internal actions of the frame. In this analysis, one-dimensional beam elements are employed irrespective of whether the cross-sections of members are slender or non-slender. However, frames composed of members with slender cross-sections may buckle in local and/or distortional modes before reaching the ultimate limit state. In this case, the flexural rigidity of the frame is reduced when local/distortional buckling occurs, and as a result it undergoes larger sway deflections than had local/distortional buckling not occurred. The additional second order moments thus caused by local/distortional bucking are not accounted for in current design provisions.

In this paper, the additional second-order effects caused by the development of local/distortional buckling are studied by comparing numerically determined ultimate capacities with design capacities. The numerical ultimate strengths are based on previously calibrated geometric and material nonlinear shell finite element models, and the design capacities are determined using the Australian Standard for Cold-formed Steel Structures AS/NZS 4600. A simplified approach to account for local/distortional buckling in beam-element-based design is also proposed. The focus is on portal frames subject to in-plane sway failure.