Experimental And Theoretical Study Of Axial Compression Long Columns Made From High Strength Cold-Reduced Steels

The use of high strength cold-reduced steels is increasing rapidly abroad. But in Chinese existing Specification GB50018-2002, there are no specific rules for the design of members made from high strength cold-reduced sheet steel.A total of 30 axial compression box-shaped long columns which were made from a thickness of 0.60mm high strength cold-reduced sheet steel were tested between pinned ends over a range of length from 400mm to 2200mm.The result of the experiment shows that it is much unconservative for the design of compression long columns if according to existing Chinese Specification GB50018-2002. So a method which considers the worse influence from low strain-hardening of high strength steel and significant interaction between local buckling and overall buckling by adding up the slendemess of columns was proposed. And a simplified formula for the calculation of reduced slendemess λc was also presented and by which long compression columns' strength can be predicted successfully.Normally one of three basic types of buckling, local, overall, and distortional can occur in high strength cold-reduced steel sections. However, the basic types may interact with each other. So the paper also research into the interaction buckling between local buckling and overall buckling by introduce into the DSM (Direct Strength Design Method) which was a entire new design method in the field of cold-formed thin-wall steel structures. The result of the calculation by DSM further confirms the correctness of the proposed method which was proposed by this paper for designing compression columns made of high strength cold-reduced sheet steels. At the same time, by comparison with the traditional Effective Width Method (EWM) the advantages of the DSM together with the Finite Stripe Method (FSM) software CUFSM while analyzing the interaction buckling of cold-formed thin-wall steel structures can be seen obviously.