Research On Local And Local-overall Buckling Behavior Of Q550 Welded I-section Members Under Axial Compression

With the constant progress of productive-processing technique of steel, the use of high strength steel has been increasing rapidly in steel structures at home and overseas. High strength steel has characteristics of higher yield and ultimate strength which makes it possible to choose steel members with smaller section under the same stress condition, thus enlarging architectural space and reducing welding and transportation. These advantages make high strength steel a better economic benfit. 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 (GB50017-2003), the strength of high strength steel can not be fully utilized when the component is unstable. The research on the local and local-overall buckling of high strength under axial compression seems more urgent.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 I-section members made of Q550 were examined. Based on the experimental data and the results of other scholars, new simplified model for residual stress distribution of the section was presented.(2) Based on the domestic Q550 high strength steel, a total of 13 mechanical performance tests,12 local stability tests and 8 local-overall stability tests of welded I-section members under axial compression were carried out. These Test results were compared with calculated values by design formulas from various codes for design of steel structures.(3) Finite element analysis was performed in this paper to investigate the local and local-overall buckling behavior of welded I-section members under axial compression, where the initial geometric imperfection and residual stress were accurately described.(4) Using the validated finit element models, parameter analyses of local and local-overall stability of welded I-section members under axial compression were carried out, with influence of main factors on the stability and bearing capacity of Q550 high strength steel column studied. Numerical simulations on a total of 211 welded I-section members under axial compression members for local stability and 232 members for local-overall stability were carried out.(5) Based on the experimental research and finite element analysis, calculation formulas based on direct strength method were developed for local and local-overall stability of Q550 high strength steel welded I-section members under axial compression.