Local And Local-overall Buckling Behavior Of Q550 High Strength Steel Welded Members Under Axial Compression

With the increase of the yield strength of steel, bearing capacity of axial compression members is more obviously controlled by stability rather than intensity. Due to the strict limitation on the width-thickness ratio of the compression members in the design formula of Code for Design of Steel Structures (GB50017), the strength of high strength steel can not be fully utilized when the component is unstable. By means of experiment test and numerical analysis, the residual stress distributions, the local and local-overall buckling behavior of Q550 high strength steel members under axial compression were investigated, with new design proposals presented. The main research works covered in this dissertation include:(1) Using the segmentation method, the residual stress of 7 welded box columns made of Q550 high strength steel were examined. Based on the experimental data and the research results of the domestic and foreign scholars, new simplified model for residual stress distribution of the section was presented.(2) Based on domestic Q550 high strength steel, a total of 5 mechanical performance tests,12 local buckling behavior tests and 10 local-overall buckling behavior tests of welded box column were carried out. Test results were compared with calculated values by design formulas from various codes for design of steel structures.(3) Considering material nonlinearity, initial geometric imperfection and residual stress, finite element models of high strength steel columns were established by finite element software ANSYS. By comparing the finite element method simulation results with test results, the reliability and accuracy of the finite element models were validated.(4) Using the validated finit element models, parameter analyses of local and local-overall buckling behavior of welded box members were carried out, with influence of main factors on the stability and bearing capacity of Q550 high strength steel column studied.(5) Numerical simulations on a total of 129 welded box axial compression members for local buckling behavior and 116 members for local-overall buckling behavior. Based on the experimental research and finite element analysis, proposed calculation formulas based on direct strength method were developed for local and local-overall buckling behavior of Q550 high strength steel welded box axial compression members. The formulas also were compared with relevant calculation formulas from various codes for design of steel structures.