Finite Element Nonlinear Analysis On Distortional Buckling Of High Strength Cold-Formed Steel Columns

Recently, the use of high strength cold-formed thin-walled sections with nominal yield stress of 550 MPa is increasing rapidly in low-rise and multi-story residential buildings and portal steel frame structures in developed countries. The design rules in our existing specification GB50018-2002 are for Q235, Q345 and not prescribe definitely for high strength cold-formed steel for the lack of the experimental and theoretical studies. With the cold-formed thin-walled steel members tending to higher strength,thinner and more complicate shaped sections,distortional buckling has become an important research topic recently in the field of international research of cold-formed steel.Based on consulting a lot of documents and the tests, This paper mainly presents detailed results on the compression stability ultimate load bearing capacity of high strength cold-formed axial compression column by nonlinear finite element analysis program ANSYS. The paper includes the following main contents:(1) A finite element model was established using ANSYS which could consider geometric and material non-liearity.A finite element analysis of the distortional buckling behavior of specimens is carried out.The finite element method models were then verified by the experimental results in terms of ultimate load-carrying capacity, falure modes. The numerical calculating results agree well with the test data.(2) Some parameters were simulated using ANSYS, the effect of web width, flange width,the width of lips, length,thickness, initial geometry imperfection and the decrease of the height for high strength cold-formed steel columns on the load carrying capacity and buckling modes is analyzed.(3) Based on the numerical analysis, combined with the Direct Strength Method, a simplified formula is suggested for calculating the the stability factor of high strength cold-formed steel columns under axial compression.