Experimental Study on Dynamic Shear Behavior of RC Beams with Different Shear-Span Ratios at Various Loading Rates

The mechanical properties of reinforced concrete (RC) beams are significantly affected by the loading rate, and a high loading rate will also stimulate the shear effect of RC beams, which may change the failure mode of RC beams. First, an MTS electrohydraulic servo system was used to carry out the cyclic loading test of four loading rates on the RC beams with three shear-span ratios respectively. The effects of the loading rate and shear-span ratio on the strength, deformation, ductility, stiffness degradation, energy dissipation capacity, and residual deformation of RC beams were studied. Second, a noncontact video measuring system was used to calculate the first principal strain of concrete on the surface of RC beams. The development and evolution of surface cracks were discussed, and the influence of loading rate on the failure mode of RC beams was further studied. Finally, the yield coefficient was introduced to modify the calculation formula of the shear strength of RC beams, and the correctness of the modified formula was verified by comparing it with the test results. The results show that the mechanical properties of RC beams are significantly affected by loading rate, similar to the shear-span ratio. The high loading rate also affects the failure mode of RC beams, transferring from flexural shear failure mode to shear failure mode. The modified formula can accurately predict the shear strength of RC beams under flexural shear failure and shear failure.