Experimental study and finite element damage modelling of concrete-filled structural elements under pure bending

This study investigates the cyclic behaviour of square concrete-filled steel tubes (CFTs) under pure bending through a combined experimental and numerical approach. Eight square CFT specimens with varying width-to-thickness ratios were tested under cyclic and constant displacement amplitude conditions to evaluate load-deformation responses, failure modes, and ultimate strength. The experimental results provided valuable insights into strength degradation and energy dissipation capacity over multiple cycles. A detailed finite element model (FEM) was developed using ABAQUS software to replicate the experimental behaviour with high accuracy. The model incorporated concrete crushing and steel ductile damage, utilizing the element deletion technique to simulate material fracture. The FEM achieved an error margin below 7 % in energy dissipation prediction, demonstrating strong agreement with experimental results. Additionally, an analytical relationship was proposed to estimate displacement at failure, offering a practical tool for future FEM simulations. This study enhances the understanding of the cyclic flexural behaviour of square CFTs, providing robust data and validated modelling techniques for structural design and performance evaluation.