Influence of rubber content on enhancing the structural behaviour of beam-column joints

This investigation aimed to determine the optimum percentage of crumb rubber (CR) in self-consolidating concrete (SCC) to enhance the structural behaviour of beam-column joints under reverse cyclic loading. The investigated mixtures were developed with percentages of CR ranging from 0% to 25%. The beam-column joint contained 2% flexural reinforcement and 0.6% shear reinforcement. The structural behaviour of the tested beam-column joints was evaluated based on load deflection, initial stiffness, rate of stiffness degradation, failure mode, cracking behaviour, displacement ductility, brittleness index, energy dissipation, first crack load and load-carrying capacity. The results indicated that the optimum percentage of CR to be used in beam-column joint mixtures is 15%. Although using this percentage slightly reduced the load-carrying capacity, it greatly enhanced the ductility, brittleness index, deformability and energy dissipation. The results also showed that further increase in the percentage of CR (above 15%) changed the failure mode of the tested specimens and limited the deformation capacity, which negatively affected the ductility, brittleness index and energy dissipation.