Seismic behavior of recycled aggregate concrete beams under cyclic torsion

Although the material property and structural behavior of recycled aggregate concrete (RAC) have been widely investigated, the research on seismic performance of RAC members under cyclic torsion is still very limited. In this paper, the failure mode, hysteresis loop, strain of steel reinforcement, principal strain of concrete, energy dissipation capacity, skeleton curve, deterioration of stiffness and ductility factor of RAC beams and natural aggregate concrete (NAC) beams under cyclic torsion were compared and investigated. The results indicate that although both the RAC and NAC torsional beams present a torsional failure mode with spiral cracks, the cracks of RAC beams are larger than that of NAC beams. The hysteresis loop shape and corresponding inflection points of NAC and RAC torsional beams are very similar, but the energy dissipation capacity and ductility factor of RAC torsional beams are about 20% and 7% higher than those of NAC beams, respectively. The use of RAC in cyclic torsional beams does not bring apparent influence on the deterioration of stiffness, but the bearing capacity of RAC torsional beams is lower than that of NAC beams.