Experimental investigation of roll-formed aluminium lipped channel beams subjected to combined bending and web crippling

Aluminium lipped channel (ALC) beams in the construction industry are becoming more popular due to their unique mechanical characteristics of durability and high strength-to-weight ratio. However, the elastic modulus of aluminium is only one third that of steel. Hence the ALC beams can buckle easily under shear, web crippling and bending actions. In the past, the structural behaviour of ALC beams under shear, web crippling and bending actions was investigated in isolation. For practical applications, however, the structural behaviour of ALC beams under combined actions should be investigated so that rational design rules can be developed. Recently, a research study was conducted at Griffith University to investigate the structural behaviour and design of ALC beams subjected to combined bending and shear actions. In the current study, an experimental program was conducted focussing on the structural behaviour and design of ALC beams subjected to combined bending and web crippling actions. Specifically, a series of tests was performed at Griffith University using ALC beams to investigate the behaviour and strengths of such sections subjected to combined bending and web crippling under unfastened interior one flange (IOF) loading conditions. Different interaction factors were selected to study the interaction levels of the bending moment and web crippling strengths of ALC beams. The length of ALC specimens in combined actions is non-dimensionalised based on the ultimate capacities of such beams subjected to pure bending and pure web crippling. The results from the combined bending and web crippling tests were then compared with the current design rules of AS/NZS 4600, AISI S100, and Eurocode 3 Part 1.3 based on the linear interaction equations, to verify their accuracy in predicting the capacities of ALC beams under combined bending and web crippling actions.