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.