冷弯薄壁型钢轴压构件畸变与整体相关屈曲研究

The behavior of cold-formed steel structures can be complicated due to the thin-walled nature of the sections. Thin-walled members of open cross-sections can display highly sensitive structural instabilities, such as local (L), Euler (E) and distortional (D) buckling, which often play a decisive role in structural behavior and govern the ultimate strengths of the members. It is well known that thin-walled members exhibit stable local and distortional post-buckling behaviors with high and middle post-critical strength capacity. At some cases, because commonly used members sometimes exhibit geometries associated with rather similar buckling stresses, their overall structural behaviors are likely to be interacted with other buckling modes. Due to the complexity of distortional behavior, researchers have not formed a popular viewpoint on how to deal with this problem. At present, research is focused on the behavior of distortional mode, but research on the interaction behavior with distortional has not been studied deeply. Especially, the interaction of distortional and Euler buckling has not investigated systematically. The interaction behavior of distortional and Euler mode will be investigated in detail in this research. Instability mechanism, failure modes, and bearing capacity of the columns will be investigated by experiment, theoretical analysis and numerical methods. Theorical models on the interaction of the distortional and global flexural, tortional and flexural-tortional model will be proposed, and the instability mechanism and deformation behavior will be explicitly identified. A criterion of identification of D, E and D+E will be proposed, and correspondingly critical condition will be presented. A novel design theory and simplified design formulae will be developed.

薄壁截面特性使冷成型钢结构的失稳力学行为更加复杂，开口截面冷弯薄壁型钢构件更容易发生局部、整体和畸变屈曲。局部和畸变都具有屈曲后强度，在一定条件下会与其他屈曲模式相关，且相关屈曲的极限承载力较低。由于畸变屈曲行为的复杂性，国内外学者对于畸变屈曲方面的研究还没有形成统一的认识。目前的研究主要集中于畸变屈曲，而对畸变相关屈曲的研究仍不深入系统，特别是畸变与整体相关屈曲的研究还未系统开展。本项目将对冷弯薄壁型钢受压构件畸变与整体相关屈曲进行系统深入的研究。采用试验研究、理论分析和数值模拟相结合的方法，对其失稳力学机理、破坏模式、极限承载力进行研究。建立畸变与整体弯曲、扭转、弯扭相关屈曲模式的理论分析模型，明确其力学机理和变形特征；提出能识别畸变屈曲、整体屈曲、畸变与整体相关屈曲的判定准则，给出相应的临界条件；提出畸变与整体相关屈曲的设计理论和简化计算方法。

薄壁截面特性使冷成型钢结构的失稳力学行为更加复杂，开口截面冷弯薄壁型钢构件更容易发生局部、整体和畸变屈曲。局部和畸变都具有屈曲后强度，在一定条件下会与其他屈曲模式相关，且相关屈曲的极限承载力较低。国内外学者对于畸变屈曲方面的研究还没有形成统一的认识，特别是畸变与整体相关屈曲的研究未系统开展。本项目对冷弯薄壁型钢受压构件畸变与整体相关屈曲性能进行研究，对其失稳力学机理、破坏模式、极限承载力进行研究。建立了畸变与整体相关屈曲模式的理论分析模型；提出了识别畸变屈曲、整体屈曲、畸变与整体相关屈曲的判定准则，给出了相应的临界条件；提出了畸变与整体相关屈曲的设计理论和简化计算方法。. （1）通过有限元精细化分析模型对冷弯薄壁C型钢轴压构件进行了相关屈曲模式及其发生的力学机理、变形特征；研究了截面几何参数对畸变与整体相关屈曲行为的影响；提出了畸变与整体相关屈曲的理论分析模型。. （2）对不同截面尺寸的68个冷弯薄壁型钢构件（包括腹板开洞情况）进行极限承载力试验研究。研究了构件畸变屈曲后与整体屈曲相互作用的承载力性能；研究了构件畸变与整体相关屈曲的变形模式、截面几何参数对畸变与整体相关屈曲行为的影响，畸变屈曲后与整体屈曲相互作用的极限承载力。. （3）研究畸变与整体相关屈曲构件的设计理论与设计方法。对当前国际上流行的直接强度法（DSM）畸变与整体相关屈曲计算公式，通过收集实验数据库进行了研究，提出了相应的设计理论和计算方法，并给出了判定准则。