Advanced Nonlinear Modelling Of Stub Recycled Aggregate Concrete-Filled Steel Tube Columns Under Axial Compression
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Recycled aggregate concrete-filled steel tubes consist of outer steel tubes filled with recycled aggregate concrete, produced from aggregates obtained by crushing construction and demolition waste. These structural members are designed to enhance the performance of recycled aggregate concrete, as its mechanical properties improve when cast into circular steel tubes, creating a 3D stress state. Under axial compression, these columns exhibit increased structural capacity due to the confinement effect of the outer steel tube and improved ductility in post-peak behaviour. This paper presents a numerical analysis of the structural response of these still-pioneering composite elements. It details the computational procedure used to calibrate the constitutive models and parameters of both steel and recycled aggregate concrete, essential for accurate numerical analysis of these columns. The proposed models modify the stress-strain relationships defined in Eurocodes 3 and 2 for steel and concrete, respectively. The procedure involves developing a 3D finite element model in ABAQUS via a Python script, combined with Bayesian optimisation in MATLAB. Finally, the most influential parameters in the steel and recycled aggregate concrete models, identified through this process, are proposed.