Design rules for web crippling of CFRP strengthened aluminium rectangular hollow sections

Web crippling failure (web buckling and web yielding) is critical for thin-walled members when subjected to concentrated load. Carbon fibre reinforced polymer (CFRP) is attracting increasing research interest as a strengthening material for metallic structural members. Improved web crippling capacity of aluminium rectangular hollow sections has been achieved with CFRP being attached to the exterior and/or interior of the webs from a series of tests conducted by the authors. This paper focuses on developing design rules for predicting the nominal crippling strength of CFRP strengthened sharp-corner aluminium tubular sections: rectangular hollow section (RHS) and square hollow section (SHS), under end bearing load. The existing design rules for bare sections without CFRP strengthening are firstly reviewed and assessed, including design rules for both cold-formed steel structural members (Australian/New Zealand standard (AS 4100-1998) and North American Specification) and aluminium structures (Australian/New Zealand standard (AS 1664-1997) and American aluminium design manual). They are modified to take account of the improved capacity due to CFRP strengthening. The proposed design rules are calibrated against test results.