Abstract
This study investigates the performance of rubberised concrete (RuC) infilled built‐up cold‐formed steel (BCFS) sections under axial compression. A total of 30 specimens were tested, including concrete cubes, cylinders, and BCFS members infilled with three concrete mixes containing 0%, 20%, and 40% rubber particles by volume. The rubber, sourced from recycled car and bicycle tyres, replaced part of the natural aggregates to enhance ductility and energy absorption. The experimental programme employed displacement‐controlled loading in combination with digital image correlation (DIC) to capture full‐field strain and deformation patterns. Results from concrete materials tests showed significant reductions in mechanical properties. For BCFS columns, the presence of RuC infill substantially improved load‐carrying capacity compared to bare steel sections, with maximum strength increases of up to fivefold. Additional nonlinear numerical validation studies are undertaken to obtain a detailed insight into the internal force distributions and steel‐concrete interface response. These findings highlight the potential of RuC‐infilled BCFS members in applications where comparatively higher deformation capability is needed.