Cold-formed steel (CFS) columns are subject to distortional buckling unlike hot-rolled steel columns. Many experimental and numerical investigations have been conducted on the distortional buckling behaviour and capacity of CFS columns at ambient and elevated temperatures. However, constitutive laws of CFS at ambient and elevated temperatures are different with varying levels of nonlinear stress-strain characteristics. Thus, the ultimate distortional buckling capacities predicted by the elevated temperature design rules can be unconservative when the ambient temperature design equations are used with elevated temperature mechanical properties. However, no study has fully incorporated the effects of nonlinear stress-strain characteristics of CFS at elevated temperatures. Therefore, this research study investigated the effects of nonlinear elevated temperature stress-strain characteristics on the distortional buckling capacities of CFS columns using three parameters, namely, nonlinearity, strain hardening and yield strength to Young's modulus ratio, through a numerical parametric study. A comparison of ultimate capacities from the parametric study with those predicted by the current AS/NZS 4600 direct strength method (DSM) showed that the current design equations cannot accurately capture the effects of nonlinear elevated temperature stress-strain characteristics. Consequently, modified DSM equations were proposed to accurately predict the distortional buckling capacities of CFS columns at elevated temperatures.

与热轧钢柱不同，冷弯型钢 (CFS) 柱会发生扭曲屈曲。已经对 CFS 柱在环境温度和高温下的扭曲屈曲行为和承载力进行了许多实验和数值研究。然而，CFS 在环境温度和高温下的本构定律是不同的，非线性应力应变特性的水平不同。因此，当环境温度设计方程与高温机械性能一起使用时，由高温设计规则预测的最终变形屈曲能力可能是不保守的。然而，没有研究完全纳入高温下 CFS 的非线性应力-应变特性的影响。所以，本研究使用三个参数，即非线性、应变硬化和屈服强度与杨氏模量比，通过数值参数研究，研究了非线性高温应力-应变特性对 CFS 柱扭曲屈曲能力的影响。参数研究的极限承载力与当前 AS/NZS 4600 直接强度法 (DSM) 预测的极限承载力的比较表明，当前的设计方程无法准确捕捉非线性高温应力应变特性的影响。因此，提出了改进的 DSM 方程来准确预测 CFS 柱在高温下的扭曲屈曲能力。