冷弯薄壁型钢拼合柱失稳机理与承载力通用设计方法研究

The cold-formed steel built-up column which consists of several C and U section members and connected by self-drilling screws has been widely applied in engineering practice. However, such a built-up column can’t behave as a whole section member when subjected to axial compression, which causes its buckling mechanism very complex due to the non-rigid screw connection. In this condition, there seems to have no research concerning the real buckling mechanism of cold-formed built-up column, and thus experimental and theoretical investigations are conducted, including (1) the real buckling mechanism of built-up columns are system revealed with respected to three levels, namely the screw built-up plate, buckling correlation of the section plate groups and member, respectively (starting from the classical theory, considering the shear slip effect, establishing a screw built-up plate stability calculation theory); the basic rules of various kinds of buckling behavior are studied, the calculation theory of complex interactive buckling is put forward; a theoretical model for the overall instability of the built-up column is established and the corresponding calculation theory is put forward, (2) based on the above research, the general bearing capacity design method of cold-formed steel built-up column is put forward. The research results of the project can provide scientific basis for the establishment of relevant design standards, which are meaningful for improving our scientific and technological innovation capability in this field.

以若干个C型、U型构件为基本单元，通过自攻螺钉连接形成的“冷弯薄壁型钢拼合柱”已广泛应用于工程实践，但此类“拼合”柱的截面并非一个整体，在轴向受压时，因受螺钉连接的非刚性、拼合截面板组间的屈曲相关性等多因素影响，力学行为十分复杂，目前对其真实的失稳机理、通用设计方法尚无研究成果。本项目以拼合轴压柱为研究对象，采用理论和试验研究相结合的方式：（1）从螺钉拼合板、截面板组相关性和构件三个层次，系统揭示此类拼合柱的真实失稳机理，主要包括：从经典理论出发，考虑“剪切滑移”影响，建立“螺钉拼合板”稳定计算理论；研究拼合柱各类屈曲的基本规律，提出考虑拼合截面“板组效应”的复杂屈曲相关计算理论；建立拼合柱的整体失稳理论模型，提出相应的计算理论；（2）在前述基础上，提出冷弯薄壁型钢拼合轴压柱的通用承载力设计方法。项目研究成果可为编制相关设计标准提供科学依据，并对提升我国在该领域的科技创新能力意义显著。

由于我国人均土地资源占有量少，把技术相对较为成熟的冷弯薄壁型钢（CFS）低层住宅结构体系推广应用到“CFS多层”结构中是发展的必然趋势。在多层CFS结构中，传统的单肢构件已不能满足受力要求，工程界常以若干冷弯薄壁C型钢、U型钢为基本单元，通过自攻螺钉连接形成“冷弯薄壁型钢拼合构件”，但此类“拼合”构件的截面并非一个整体，作为柱子在轴向受压时，因受螺钉连接的非刚性、拼合截面板组间的屈曲相关性等多种因素影响，其力学行为十分复杂。目前，对其真实的失稳机理、通用设计方法等关键问题尚无研究成果。本项目以冷弯薄壁型钢拼合轴压柱为研究对象，采用理论和试验研究相结合的方法：（1）从螺钉拼合薄钢板板、截面板组相关性和构件三个层次，系统揭示此类拼合柱的真实失稳机理，主要包括：从经典理论出发，考虑“剪切滑移”影响，建立“螺钉拼合板”稳定计算理论；研究了拼合柱各类屈曲的基本规律，提出考虑拼合截面“板组效应”的复杂屈曲相关计算理论；建立拼合柱的整体失稳理论模型，提出相应的计算理论；（2）在前述基础上，提出冷弯薄壁型钢拼合轴压柱的通用承载力设计方法。通过本项目的研究，较为系统性地形成了冷弯薄壁型钢拼合截面轴压柱的稳定分析理论和承载力通用设计方法，全套分析理论和设计方法的建立可为国家、行业、地方标准的编制提供科学依据，促进CFS多层房屋结构的应用与发展，为建筑行业的“碳达峰和碳中和”提供技术支撑。