Abstract
In order to examine safety over shear failure of RC beams subjected to impact loadings, it is essential to investigate the influence of loading rate on the shear resistance of RC beams and to develop an analytical model to evaluate it. Therefore, this paper initially presents an experimental investigation through rapid loading tests for RC beams with a shear span-to-depth ratio of 3.3 to clarify the effects of loading rates and shear reinforcement ratios on the failure modes and ultimate resistance of the RC beams. It was found that the RC beams without shear reinforcement exhibited diagonal tension shear failure under all the loading rates, while the failure modes were changed from brittle shear failure to ductile flexure failure by increasing the shear reinforcement ratios. The influence of loading rates on the ultimate resistance of the RC beams was more significant in shear failure than in flexure failure. Subsequently, well-known Modified Compression Field Theory (MCFT) developed under static loading was extended to the dynamic loading to evaluate the dynamic shear resistance of RC beams. The developed dynamic MCFT was justified by comparing with the experimental data. Finally it was found that the dynamic increase ratios in the shear resistance of RC beams calculated from the dynamic MCFT were consistent with those in the dynamic shear strength of concrete.
