Mesoscopic analysis on size effect of dynamic shear response of RC beams under low-velocity impact

Abstract

The size effect on dynamic shear responses of RC beams is important for evaluating the impact resistance of practical structures, while the related studies remain limited. Thus, this study aims to systematically examine the size effect in shear-failure RC beams and establish similarity relationships for dynamic shear responses. Firstly, a mesoscopic finite element (meso-FE) model is developed and validated through dynamic loading tests on small and large RC beams, accurately reproducing the dynamic shear capacity, impact force, mid-span deflection, and failure modes. Then, the deflection instead of the shear crack width is recommended as a quantitative index for damage evaluation in shear-failure RC beams. The mesoscopic simulation analysis reveals that the normalized maximum deflection of stirrup-reinforced beams could increase by approximately 23.7 % when the scale factor ranges from 1 to 6. Furthermore, the parametric analyses demonstrated that the stirrup ratio exerts the most significant influence on the size effect, with the increase factor of normalized maximum deflection reaching 211.1 % for beams without stirrup and the scale factor from 1 to 6. Finally, a similarity relationship for normalized maximum mid-span deflection is established by the response surface methodology, incorporating critical parameters such as impact energy, mass ratio of impactor to beam, shear span-to-depth ratio, and stirrup ratio. These findings provide a methodological framework for evaluating the impact resistance of full-scale shear-failure RC beams in practical engineering structures.