Overall buckling behaviour and design of high-strength steel welded section columns

Practical use of high-strength (HS) steel in contemporary construction has become one of the most important design solutions. Loading capacities of columns may benefit enormously from the HS steel, whilst their overall buckling behaves differently compared with conventional mild (CM) steel columns due to varying effects of initial imperfections and inelastic properties of the HS steel materials. Despite a number of investigations regarding the HS steel columns being undertaken, there is lack of research focused on variation of HS steel grades and their effects. To deepen understanding of overall buckling behaviour of the HS steel columns, a comprehensive review of an extensive body of column test data available in the literature is carried out in the present paper, based on which a three-dimensional finite element (FE) model developed herein is validated. Parametric analyses are subsequently undertaken with various HS steel grades, welded cross-sectional geometric parameters, slenderness values and initial imperfections being involved. The FE analysis results are also compared with calculation values in accordance with national standards. It has been demonstrated that with an increase of the grade of HS steel, effects of imperfections decrease whilst that of Y/T ratios are rather limited; reduction effects on the overall buckling strength become less severe, and therefore higher column curves available in current national standards may be selected and imperfection factors in the alternative column curve equations proposed herein descend accordingly. In addition, new theoretical column curves based on Perry-Robertson formula are developed by introducing imperfection parameters independent on the steel strength.