Experimental study on behavior of reinforced recycled aggregate concrete beams subjected to combined shear and torsion

In order to study the behavior of reinforced recycled aggregate concrete (RAC) beams subjected to combined shear and torsion, the static loading tests of seven RAC beams with different torsion-shear ratios and recycled coarse aggregate (RCA) replacement ratios were conducted by a self-designed loading device. The test process and failure modes were observed during the experiments. The influences of different design parameters on the performance of RAC beams under combined shear and torsion were elaborated. The results indicate that the RAC beams have a similar failure mode compared with the normal concrete beams, transitioning from the shear type to torsion type with the increase of torsion-shear ratio. As the amount of RCA replacement ratio increases, there is a reduction in the initial torsional stiffness and cracking load, and the brittle failure features become more distinct, while the bearing capacity has no obvious change. The formula in GB 50010-2010 'Code for design of concrete structures' can be used for calculating the bearing capacity for RAC beams under combined shear and torsion.