title: Structural Behaviour and Design of Aluminium Lipped Channel Beams Under Combined Actions
Creators: name: Nguyen, Anh Vy
Publisher: name: Griffith University
Year: 2022
Subjects: subject: Aluminium
subject: Lipped channel beams
subject: Combined bending and shear
subject: Experiments
subject: Finite element analysis
subject: Design rules
subject: Roll-formed
subject: Web crippling
subject: Combined actions
subject: Unfastened

description: During recent decades, the use of aluminium lipped channel (ALC) beams as purlins, and floor joists in roof and floor systems in the construction industry has significantly increased due to their superior mechanical characteristics compared to steel, such as durability, light weight, high strength to weight ratio, and being weatherproof. However, despite these advantages, the elastic modulus of aluminium is only one-third that of steel. Hence ALC beams with shorter span lengths are vulnerable to buckling failures under concentrated load, such as shear and web crippling. On the other hand, ALC beams with longer span lengths can fail due to combined actions such as bending and shear actions, and bending and web crippling actions. In the past, the structural response of ALC beams has been investigated, but only under single actions of shear, web crippling, and bending. However, the behaviour of ALC beams subjected to combined bending and shear actions, and bending and web crippling actions needs to be investigated for real-world engineering applications. To address this research gap, experimental and numerical investigations on the strength and behaviour of ALC beams subjected to two scenarios of combined bending and shear actions, and combined bending and web crippling actions were conducted, and are presented in this thesis. The first step of the research focused on experimental investigation. Subsequently, numerical investigations including validation and parametric studies were carried out. Finally, the current available design rules were assessed and new design rules were proposed where needed. The experimental study comprised four test series of pure bending, web crippling, combined bending and shear actions, and combined bending and web crippling actions, using 12 different ALC sections. All ALC beams chosen for the experimental test program were supplied by BlueScope Permalite, Australia. The test specimens were fabricated by roll-forming method using aluminium alloy 5052-H36. A total of 62 tests were conducted on the ALC specimens, consisting of six four-point bending tests undergoing local buckling; nine web crippling tests under unfastened interior-one-flange (IOF) loading condition; 24 combined bending and shear tests considering two aspect ratios (ARs) of 1.5 and 2.0; and 23 combined bending and web crippling tests considering five interaction factors of 1.0, 1.5, 2.0, 2.5 and 3.0 under unfastened IOF loading condition. In the numerical study, nonlinear finite element (FE) models of ALC beams using ABAQUS/CAE software package were developed to simulate the behaviour of such beams under pure shear, web crippling, bending and combined actions. The developed FE models were validated by comparing the finite element analysis (FEA) results with those obtained from the tests. Good agreements were achieved throughout three criteria of ultimate capacities, applied load versus vertical displacement curves, and failure modes. The developed FE models were then used to undertake a detailed parametric study to obtain a large dataset of the strengths of the ALC sections with different parameters. The ultimate capacities of ALC beams obtained from the tests and FE models were compared with those predicted using current design rules of AS/NZS 4600, including direct strength method (DSM), AS/NZS 1664.1, AISI S100, Eurocode 3 Part 1-3, and the previously proposed design equations. It was found that the current DSM was safe in predicting the ultimate bending moment capacities of ALC beams undergoing local buckling. The previously proposed design equations were reasonably reliable in predicting the shear and web crippling capacities of the ALC beams. The available design equations in the form of circular and linear interaction curves provided by AS/NZS 4600 and developed in the previous study were too conservative in estimating the combined bending and shear capacities of the ALC beams. Hence, new design equations were proposed in the current study for the accurate prediction of the capacities of ALC beams under combined bending and shear actions. The current design rules of AS/NZS 4600, AISI S100, and Eurocode 3 Part 1-3 are not suitable to predict the combined bending and web crippling capacities of the ALC beams accurately. Therefore, new design equations were developed for the accurate prediction of the combined bending and web crippling capacities of the ALC beams under unfastened and fastened IOF loading conditions.