It is highly important to clarify the high-temperature mechanical properties in the design of cold-formed steel (CFS) structures under fire conditions due to the unique deterioration feature in material properties under fire environment and associated reduction to the mechanical performance of members. This paper presents the mechanical properties of widely used steels for cold-formed steel structures at elevated temperatures. The coupons were extracted from original coils of proposed full annealed steels (S350 and S420, with nominal yielding strengths 280 MPa and 350 MPa) and proposed stress relieving annealed steels (G500, with nominal yielding strength 500 MPa) for CFS structures with thickness of 1.0 mm and 1.2 mm, and a total of nearly 50 tensile tests were carried out by steady-state test method for temperatures ranging from 20 to 700°C. Based on the tests, material properties including the yield strengths, ultimate strengths, the elasticity modulus, and the stress-strain curve were obtained. Meanwhile, the ductility of steels for CFS structures was discussed. Then, the temperature-dependent retention factors of yield strengths and elasticity modulus were compared to those provided by design codes and former researchers. Finally, a set of prediction equations of the mechanical properties for steels for CFS structures at elevated temperatures was proposed depending on existing tests data.

中文翻译：

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高温下冷弯型钢结构用钢的力学性能

由于火灾环境下材料性能的独特恶化特征以及相应的构件机械性能下降，在火灾条件下的冷弯型钢（CFS）结构设计中弄清高温机械性能至关重要。本文介绍了在高温下广泛用于冷弯型钢结构的钢的机械性能。试样是从建议的全退火钢（S350和S420，标称屈服强度为280 MPa和350 MPa）和建议的应力消除退火钢（G500，标称屈服强度为500 MPa）的原始卷材中提取的，该卷材厚度为1.0通过稳态测试方法对20至700°C的温度进行了50 mm和1.2 mm的拉伸试验，总共进行了近50次拉伸试验。根据测试，获得了包括屈服强度，极限强度，弹性模量和应力-应变曲线在内的材料性能。同时，讨论了用于CFS结构的钢的延展性。然后，将屈服强度和弹性模量与温度相关的保留因子与设计规范和以前的研究人员提供的保留因子进行了比较。最后，根据现有的测试数据，提出了一套用于高温下CFS结构钢的机械性能的预测方程。将屈服强度和弹性模量的温度相关保留因子与设计规范和以前的研究人员提供的保留因子进行了比较。最后，根据现有的测试数据，提出了一套用于高温下CFS结构钢的机械性能的预测方程。将屈服强度和弹性模量的温度相关保留因子与设计规范和以前的研究人员提供的保留因子进行了比较。最后，根据现有的测试数据，提出了一套用于高温下CFS结构钢的机械性能的预测方程。