Slenderness effects on CFRP strengthening of aluminium tubular structural members subjected to concentrated end bearing load

Abstract

Aluminium tubular structural members may experience web crippling failure due to localize concentrated loads or reactions. This paper reports an experimental program on strengthening of high strength aluminium tubular structural members using externally bonded carbon fibre-reinforced polymer (CFRP). A series of tests on CFRP strengthened aluminium square and rectangular hollow sections subjected to web crippling are presented. The web crippling tests were conducted under two loading conditions of End-Two-Flange (ETF) and End-One-Flange (EOF). A total of 27 web crippling tests were conducted in this study. The investigation was mainly focused on the effects of web slenderness of aluminium tubular sections on CFRP strengthening against web crippling. The tests were performed on eight different sizes of square and rectangular hollow sections which covered a wide range of slenderness (flat portion of web depth-to-thickness) ratio from 6.2 to 61.8. Material properties of each aluminium section were obtained from tensile coupon tests. Most of the strengthened specimens were failed by debonding of CFRP plate from the aluminium tubes. Three main failure modes were observed in the tests, namely the adhesion, combination of adhesion and cohesion, and interlaminar failure of CFRP plate. The failure modes and the load-web deformation behaviour of the aluminium sections are also presented. It was found that the web crippling capacity of aluminium sections are significantly increased due to CFRP strengthening, especially for those sections with higher web slenderness ratio.