Experimental and numerical investigation of rubberized concrete beam–column joints subjected to monotonic loading

The incorporation of waste tire rubber into structural concrete has attracted increasing attention as a sustainable approach for reducing environmental pollution while enhancing the deformation capacity and energy absorption of reinforced concrete (RC) members. However, the structural behavior of rubberized concrete beam-column joints remains insufficiently understood, particularly under monotonic loading conditions. This study presents an integrated experimental and numerical investigation of exterior RC beam-column joints incorporating crumb rubber as a partial replacement for fine aggregate. Four exterior beam-column joint specimens containing 0%, 10%, 15%, and 20% crumb rubber by volume were tested under monotonic lateral loading while maintaining a constant axial load on the column. The structural response was evaluated in terms of load-displacement behavior, ultimate load capacity, stiffness degradation, deformation capacity, energy absorption, crack development, and failure mode. A three-dimensional finite element model was developed using ABAQUS based on the Concrete Damage Plasticity (CDP) model and validated against the experimental results. The validated numerical model was subsequently employed to conduct a parametric study investigating the influence of axial load ratio on the structural performance of rubberized beam-column joints. The experimental results demonstrated that incorporating moderate amounts of crumb rubber significantly enhanced deformation capacity and energy absorption while maintaining satisfactory load-carrying capacity. The specimen containing 10% crumb rubber exhibited the best overall structural performance by providing the most balanced combination of strength, deformation capacity, and energy absorption, with only a limited reduction in ultimate strength compared with the control specimen. Numerical predictions showed excellent agreement with the experimental observations in terms of load-displacement response, cracking behavior, and failure mode. The parametric study further indicated that lower-to-moderate axial load ratios provided favorable structural performance, whereas excessive axial compression reduced the deformation capacity of the joints. The findings demonstrate that rubberized concrete can provide a practical and sustainable alternative for improving the overall structural performance of RC beam-column joints subjected to monotonic loading.