title: STRUCTURAL BEHAVIOUR AND DESIGN OF ALUMINIUM ALLOY-CONCRETE COMPOSITE STRUCTURAL MEMBERS
Creators: name: Ali, SB
Publisher: name: Liverpool John Moores University
Year: 2023

description: The use of aluminium alloys in the construction industry is rising due to their profound features including high strength-to-weight ratio, good corrosion resistance, ease of processing, low maintenance, high recyclability and aesthetic appearance. However, the low modulus of elasticity, welding difficulty and low melting point of aluminium have adverse effects on the performance of structural members made of aluminium alloys. In case of aluminium alloy tubular members, the structural performance can be improved with the addition of concrete infill, despite the different expansion of aluminium alloy and concrete. In concrete-filled aluminium tubular (CFAT) structural members, the aluminium tube increases the compressive performance of the concrete core due to the confinement effect, while the concrete core delays inward local buckling of the aluminium tube. Moreover, the self-weight of these structural members can be decreased further by replacing the inner concrete core with a hollow tube. Concrete-filled double skin aluminium alloy tubular (CFDSAT) member is made with two aluminium tubes and concrete infill between them. CFDSAT members retain all advantages of CFAT ones and additionally they have less self-weight. Moreover, these members offer better local and global stability because of the interaction of three components. Therefore, compared to steel-concrete composite members, CFDSAT members can be more efficient for structures situated in offshore areas and seismic-prone regions. However, the research on the structural performance of aluminium alloy-concrete composite members is minimal. Therefore, this study investigates the behaviour of CFAT and CFDSAT structural members subjected to axial compression and bending. In the experimental programme of CFAT structural members, a total of 18 columns, including 9 CFAT and 9 bare aluminium tubular (BAT) specimens and 20 beams, including 10 CFAT and 10 BAT specimens are tested. The BAT structural members are tested for reference purposes and to assess the applicability of Eurocode 9 design standard. The experimental investigation of CFDSAT structural members includes 8 columns and 10 beams. The column tests are conducted using a pin-ended set-up for allowing the specimens to rotate around the buckling axis. The flexural members are tested in a four-point bending arrangement to spread out the maximum stress over the area between the two loading points. The material properties of aluminium alloy are determined by tensile coupon tests. The structural responses obtained from the experiments are presented in terms of ultimate capacity, failure modes and load/moment versus mid-length defections curves. Finite element (FE) models of the structural members are developed by taking into account the geometric and material nonlinearities and validated against the experimental results. The validated models are adopted to conduct parametric studies to examine the effects of different design parameters on the behaviour of the structural members. In the absence of design rules for aluminium alloy-concrete composite structural members, design methodologies are proposed to predict the ultimate capacity of these composite members based on the Eurocode 4 framework. To obtain information about the sustainability of aluminium alloy-concrete composite structural members, the life-cycle performance of CFAT and CFDSAT columns is investigated. Life-cycle assessment and life-cycle cost analysis methods are applied to evaluate the long-term environmental and economic aspects of these members, respectively. The cradle-to-grave system boundary is considered for these analyses to cover all the aspects of life-cycle. Finally, a comparison of the self-weight of these members is also presented. The experimental results show that compared to the bare specimens, the counterpart composite specimens have remarkably improved ultimate capacity, stiffness and ductility due to the concrete infill and the improvement is more pronounced for the specimens with thinner sections. The FE parametric investigation reveals that the larger cross-sectional dimensions of the outer tube of composite members substantially improved the load-bearing capacity, while the cross-sectional dimensions of the inner tube have a negligible effect. Moreover, FE results show that higher grade concrete remarkably increased the strength of composite columns, while it has a less significant influence on the improvement of the flexural strength of composite beams. In the absence of design standards for aluminium alloy-concrete composite structural members, design methodologies are provided based on Eurocode 4 (2004) to determine the strength of these members. The self-weight comparison and sustainability study results indicate that CFDSAT structural member is lighter, while the CFAT member is less expensive and provides the lowest environmental impact than the other alternatives considered in this study.