Design of aluminium alloy stocky hollow sections subjected to concentrated transverse loads

Abstract

Web crippling is a phenomenon where section webs cripple due to a concentrated force. This phenomenon could be caused by web buckling for slender sections or by web bearing/yielding for stocky sections. The aim of this study is to investigate the web bearing design rules for relatively stocky sections. Experimental tests and numerical modelling results on aluminium alloy square and rectangular hollow sections (SHS/RHS) subjected to web bearing are presented. The tests were conducted under four loading conditions: end-two-flange (ETF), interior-two-flange (ITF), end-one-flange (EOF), and interior-one-flange (IOF). Two different bearing lengths, 50 mm and 90 mm, were investigated. The test specimens were fabricated by extrusion using 6063-T5 and 6061-T6 heat-treated aluminium alloys. Web slenderness values (i.e. the width-to-thickness ratio h / t) ranging from 2.8 to 28.0 have been considered. Non-linear finite element (FE) models were developed and validated against the test strengths and specimen failure modes. Upon validation, the FE models were used to perform a parametric study in order to supplement the experimental work. A total of 138 web bearing data consisting of 34 test results and 104 numerical results were generated in this study. In the ETF and ITF loading conditions, all specimens failed by material yielding at the webs. For the EOF and IOF loading conditions, specimens failed by flexural failure, interaction of web bearing and bending effects or material fracture at the tension flanges. The generated data is used to assess the web bearing design equations in the existing design codes as well as to propose new design rules. The new design rules for ETF and ITF loading conditions are proposed with the consideration of strain hardening effects. Further analyses have been carried out to show the newly proposed design rules are not only accurate and consistent, but also safe and reliable.