The Stability Behavior Of Cold-formed Thin-Walled Steel Members With New Cross Sections Under Compression Loading

The stability is a key problem for the design of cold-formed thin-walled steel structures. With the use of new section shapes and high strength steel plates with thinner thickness, some new stability problems are brought simultaneously. Such as, the compression load carrying capacity of members with different section shapes under interaction of local, distortional and overall buckling conditions. As well, with the style more and more complex, the distortional buckling will play a significant role in ultimate load-carrying capacity. At present, few theoretical and experimental studies about the stability behavior of the new section members under compression loading are provided. In recent years, Direct Strength Method (DSM) is attentioned by a large number of scholars, when the ultimate load-carrying capacity is calculate by Direct Strength Method, critical stress of elastic buckling is a important step. However, few theoretical about a simplified formula for calculating the elastic distortional buckling stress of cold-formed thin-walled steel members with new cross sections is studied by scholars.Aiming to the design application, the above problems are investigated by test and theoretical analysis systematically in this paper, which may give helps to a deeper understanding of the stability behavior of cold-formed thin-walled steel members with new cross sections under compression loading and provide a reasonable design guideline. As well, a simplified formula for calculating the elastic distortional buckling stress is provided.Faced with little experimental studies on the ultimate strength of pin-ended channels with new cross sections, a total of24pin-ended cold-formed steel columns with three types of length and three types of complicated sections including channels with complex edge stiffeners, Σ style and channels with complex edge stiffeners, channels with complex edge stiffeners and intermediate V type stiffeners in the web, respectively. The ultimate load-carrying capacity, buckling modes and deformation behavior of cold-formed steel members with complicated cross sections in this paper were studied. It is found that the existence of intermediate stiffeners has an obvious effect on axial compression ultimate load-carrying capacity and buckling modes. Moreover, the finite element analyses by ANSYS which considered geometric and material nonlinearities were conducted and verified against tests. It offered powerful test basis and established well foundation for the further theoretical study.A large amount of cold-formed thin-walled steel members with new cross sections are analyzed by the finite strip software CUFSM. The influence of the parameter for the elastic distortional buckling stress is analyzed. Based on the above study results for the elastic distortional buckling stress, a simplified formula for calculating the elastic distortional buckling stress of Σ style and channels with complex edge stiffeners, channels with complex edge stiffeners and intermediate V type stiffeners in the web is provided. The simplified formula can be used in the actual design.