Postbuckling resistance of high strength steel welded I-section beams based on interactive slenderness

Abstract

The steel, whose nominal yielding strength fy is greater than or equal to 460 MPa, is generally referred to as high strength steel (HSS). Through the comparison with conventional strength steel (CSS) members, HSS members are more vulnerable to local buckling since the component plates are usually designed to be more slender in order to exploit higher material strength. The different mechanical properties between HSS and CSS, including yielding strength, ductility and so on, may lead to different local buckling behavior of steel members. However, little guidance is applicable in existing standards for the stability design of HSS members. In this paper, elaborate finite element (FE) models of HSS welded I-section beams under the loading conditions of uniform moment (four-point loading) and moment gradient (three-point loading) were developed by means of the general-purpose FE software package and validated against the available test results. Continuous lateral supports were ideally applied to restrict the occurrence of coupling with overall lateral‐torsional buckling. Comprehensive parametric analyses on key parameters containing the plate width-to-thickness ratio and the steel material properties were further conducted, reflecting the influence of these parameters on the mechanical performance of local stability. Through this work, the variation rules on rotation capacity and postbuckling resistance of HSS welded I-section beams with plate width-to-thickness ratio and steel nominal yielding strength were clarified. Taking into account the interaction of local buckling modes between flanges and webs, new cross-section classification of HSS welded I-section beams was proposed based on the FE analysis results. After the introduction of the concept of interactive local slenderness, the design methods of postbuckling ultimate moment resistance for HSS welded I-section beams subjected to uniform moment and moment gradient were also proposed, which were assessed by comparing the design results with the ones obtained from the corresponding design approaches in Eurocode 3, ANSI/AISC 360–16 and GB 50017–2017. And the reliability of the new proposals was also confirmed by further statistical analysis.