Local buckling behaviour of high strength steel and hybrid I-sections

Abstract

The virtue of high strength-to-weight ratio has rendered high strength steel (HSS) structures receive increasing attention these years. I-sections (or H-sections) are one of the most common cross-sections applied as compressive and flexural members in construction. Hybrid I-sections, defined as the sections with HSS flange and lower strength web, offer more opportunities to achieve the material optimal utilisation under various scenarios. Due to thin thickness, local instability is one of the primary concerns for I-sections with HSS plate elements. This thesis focuses on the local buckling behaviour of HSS and hybrid I-section members under compression as well as under bending. Experimental investigations were performed on the local buckling behaviour of twelve I-section stub columns and eighteen I-beams. Underpinned by the test results, parametric studies using validated finite element models were carried out to identify the effect of steel material characteristics, flange slenderness and web slenderness on the local buckling behaviour of HSS and hybrid I-sections in compression or bending. Extensive numerical results were also utilised to assess the applicability of European and American codes. Furthermore, the design concept in Japanese Limit State Design of Steel Structures, the direct strength method (DSM) and the continuous strength method (CSM), all of which are capable of considering the interactive effect between flanges and web, were extended to the design of local buckling behaviour of HSS and hybrid I-section compressive and bending members.