Local-Overall Interactive Buckling Of High Strength Steel Welded I-Section Columns Under Axial Compression

In this study, the investigation on the overall-local interactive buckling performance of high strength steel welded I-section columns was carried out. Finite element models of steel columns of different yield strength (235 MPa, 460 MPa, 500MPa, 690 MPa, 800MPa, 960 MPa) were constructed considering geometric imperfection and residual stresses, and verified against the existing test results. Effect of geometric imperfection including global imperfection and local imperfection was found to be largely dependent on the nominal slenderness ratio of columns (lambda(n)). Local imperfection present prominent influence for the case of lambda(n) lower than 0.4, while global imperfection for the case of lambda(n) exceeding 0.95. Effect of four types of residual stress patterns on ultimate capacity were compared, the disparity of which was around 10%. Comprehensive effect of imperfections on local buckling load was found to be smaller resulted from higher steel grade; whilst that on stiffness became more pronounced. Based on the test data of stub columns, new predict formulas were proposed for the local post-buckling strength using effective width method and direct strength method respectively. Continuing the investigation of stub columns, the formulas for interactive buckling resistance of high strength steel welded I-section around the weak axis were studied, where column curve b in Eurocode3 was suggested to be adopted.