Cyclic torsion performance of recycled aggregate concrete beams with or without fly ash

Although the material property and structural behavior of recycled aggregate concrete (RAC) and modified RAC (MRAC) have been widely investigated, the research on seismic performance of RAC and MRAC members under combined flexure-shear-torsion cyclic loading is still very limited. In this paper, the failure mode, hysteresis loop, strain of steel reinforcement, energy dissipation capacity, skeleton curve, deterioration, stiffness and ductility factor and torsional bearing capacity calculation of RAC and MRAC beams subjected to combined cyclic torsion were compared and investigated. The results indicate that the addition of fly ash didn't bring an obvious effect to the failure mode of test beams. Although the bearing capacity of MRAC beams is lower than that of RAC beams, the ductility factor and energy dissipation capacity of MRAC beams are larger than those of RAC beams. The addition of fly ash will weaken the hysteretic performance to some extent. The larger the torsion-shear ratio is, the more serious deterioration of stiffness is. The addition of fly ash does not bring apparent influence on the deterioration of stiffness. The variable angle space truss model was employed to calculate the torsional bearing capacity of RAC and MRAC beams subjected to combined cyclic torsion. The predictions agree well with the test results of the torsional beams.