冷弯薄壁型钢轴压构件畸变与整体相关屈曲承载力计算方法研究

Calculation-method investigation on ultimate load-carrying capacities of cold-formed steel columns experiencing distortional-global buckling interaction under axial compression

基于我国《冷弯型钢结构技术规范》(征求意见稿)和北美规范及澳洲/新西兰规范中的直接强度法,利用国内外已有的试验数据,计算了60根破坏模式为畸变与整体相关屈曲的轴压试件以及50根破坏模式为畸变屈曲的轴压试件的承载力。通过计算值与试验值的对比分析表明:我国《冷弯型钢结构技术规范》(征求意见稿)中直接强度法所计算的轴压试件畸变与整体相关屈曲的承载力与试验值之比的平均值接近1.0,结果较为理想;计算所得的轴心受压试件畸变屈曲的承载力明显高于试验值,偏于不安全。基于上述结果,对《冷弯型钢结构技术规范》(征求意见稿)中直接强度法计算畸变屈曲的承载力提出了相应建议,即畸变与整体相关屈曲的承载力计算公式和畸变屈曲的承载力计算公式不应统一,应区别对待或给出附加核查条件,在计算畸变半波长度和畸变屈曲的承载力时,采用屈服荷载而非构件整体稳定承载力。

This paper describes a calculation-method investigation on ultimate load-carrying capacities of cold-formed steel columns under axial compression. Based on the existing test data in the literatures, the ultimate load-carrying capacities of 60 steel columns experiencing distortional-global buckling interaction and 50 steel columns experiencing distortional buckling were calculated by using the revised direct strength method in the Chinese code ‘Technical code of cold-formed steel structures(exposure draft)’ and the direct strength method in the North American specification or standards of Australia/New Zealand. Comparing the calculated results with the experimental results, it is found that in terms of the ultimate distortional-global buckling interaction resistance, the mean value of the ratios of calculated value to experimental value is close to 1.0 on the unsafe side when the revised direct strength method in Chinese code is considered. For the ultimate distortional buckling resistance, the calculated values are significantly higher than the experimental results, rendering unsafe design. Based on the above findings, it is recommended that when calculating the ultimate distortional buckling resistance, the formula of the distortional-global buckling interaction and distortional buckling resistance should not be shared. The yield load rather than the global instability resistance should be adopted for calculating the length of half-wave and the distortional buckling resistance.