Current design rules for the member capacities of cold-formed steel columns are based on the same non-dimensional strength curve for both fixed and pinned-ended columns at ambient temperature. This research has investigated the accuracy of using current ambient temperature design rules in Australia/New Zealand (AS/NZS 4600), American (AISI S100) and European (Eurocode 3 Part 1.3) standards in determining the flexural-torsional buckling capacities of cold-formed steel columns at uniform elevated temperatures using appropriately reduced mechanical properties. It was found that these design rules accurately predicted the member capacities of pin ended lipped channel columns undergoing flexural torsional buckling at elevated temperatures. However, for fixed ended columns with warping fixity undergoing flexural-torsional buckling, the current design rules significantly underestimated the column capacities as they disregard the beneficial effect of warping fixity. This paper has therefore recommended the use of improved design rules developed for ambient temperature conditions to predict the axial compression capacities of fixed ended columns subject to flexural-torsional buckling at elevated temperatures within AS/NZS 4600 and AISI S100 design provisions. The accuracy of the proposed fire design rules was verified using finite element analysis and test results of cold-formed lipped channel columns at elevated temperatures except for low strength steel columns with intermediate slenderness whose behaviour was influenced by the increased nonlinearity in the stress-strain curves at elevated temperatures. Further research is required to include these effects within AS/NZS 4600 and AISI S100 design rules. However, Eurocode 3 Part 1.3 design rules can be used for this purpose by using suitable buckling curves as recommended in this paper.
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机译：当前冷弯型钢构件承载力的设计规则基于在环境温度下固定和固定端的相同的无量纲强度曲线。这项研究调查了使用澳大利亚/新西兰（AS / NZS 4600），美国（AISI S100）和欧洲（Eurocode 3 Part 1.3）标准的当前环境温度设计规则确定冷弯弯曲屈曲屈曲能力的准确性。使用适当降低的机械性能在均匀的高温下成型钢柱。已经发现，这些设计规则准确地预测了在高温下经受弯曲扭曲屈曲的销钉端部带槽通道柱的构件容量。但是，对于翘曲固定性经受挠曲-屈曲屈曲的固定端立柱，当前的设计规则忽略了翘曲固定性的有益影响，因此大大低估了柱的承载能力。因此，本文建议使用针对环境温度条件开发的改进设计规则，以预测AS / NZS 4600和AISI S100设计规定中在高温下经受挠曲-屈曲屈曲的固定端柱的轴向压缩能力。通过有限元分析和高温下冷弯唇形槽柱在高温下的测试结果，验证了所提出的消防设计规则的准确性，但中等细长的低强度钢柱的行为受到应力-应变曲线非线性度的增加的影响在高温下。需要进一步研究，以将这些影响包括在AS / NZS 4600和AISI S100设计规则中。但是，通过使用本文推荐的合适的屈曲曲线，可以将Eurocode 3 Part 1.3设计规则用于此目的。
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