Local Buckling And Design Method Of High Strength Steel Welded-Section Members Under Axial Compression

With the development of steel structures, the use of high strength steel inbuilding constructions has been increased very rapidly. High strength steel oftenleads to lighter and thinner sections, with the same compressive strength andoverall stability. Hence local buckling becomes more critical for high strengthsteel members under axial compression, especially for those with smallslenderness and relatively large width-to-thickness ratios. This paper isconcerning with the local buckling behavior of high strength steel welded squarebox section and I-section members under axial compression, and the finiteelement models to analyze. The main results are as following:(1) Axial compression experiments of460MPa and960MPa high strengthwelded square box section and I-section stub columns were conducted.Mechanical data of steel columns, local buckling loads and ultimate loads areobtained. Through the study on the curves of load to displacement, it’sconcluded that local buckling has influence on the bearing capacity of thecolumn, but has little influence on the axial stiffness.(2) Based on the test results in this paper and other papers, whether theformulas of the embedded coefficient, the local buckling stress and the ultimatestress in Chinese, American, European, Australia and British steel structuredesign codes are applicable to high strength steel welded box section andI-section columns is discussed. It’s concluded that all the formulas are notapplicable to high strength steel columns.(3) Finite element analysis was performed in this paper to investigate thelocal buckling strength, the ultimate strength of welded box section andI-section columns under axial compression, where the residual stresses and theinitial geometric imperfections of specimens were accurately described. And thefinite element analysis results are compared with the test results.(4) By using the validated finite element model, the finite elementparametric analysis is conducted on the local buckling behavior of welded boxsection and I-section columns under axial compression, including the ratio ofwidth to thickness of steel plate, the ratio of length to width of steel plate, the thickness of steel plate, the yield strength of steel plate, the initial geometricimperfection.(5) With the finite element analysis results of welded box section andI-section columns under axial compression, the advised design formulas of localbuckling stress and ultimate stress are proposed, which take into account theeffects of steel strength and the ratio of width to thickness of steel plate.Compared with the test results, it’s concluded that the proposed design formulasare applicable to high strength steel welded box section and I-section columns.(6) With the proposed design formulas of local buckling stress, the adviseddesign formulas of the limit ratio of width to thickness of steel plate areproposed.