Dynamic shear force-bending moment interaction diagrams in RC beams under impact

Civil structures and buildings may be subjected to accidental impact load scenarios to which the response is still a research subject. Impact failure mode and resistance of concrete structures have shown to be rather different from those under quasi-static loading, due to the influence of strain-rate modification of material properties, development of inertia forces leading to variable sectional forces' distributions and local damage mechanisms. A high sensitivity to develop shear-related failures of reinforced concrete beams under impact loading has been observed experimentally, with a complex shear-bending interaction difficult to be modelled numerical and analytically. Shear force-bending moment (M-V) interaction diagrams have been traditionally employed to provide the combination of sectional forces leading to failure. Thus, the availability of such diagrams for impact scenarios would be very useful for the engineering practice. In the present paper, an experimental investigation is presented to analyze the impact resistance of reinforced concrete beams with different span-to-depth ratios in order to determine possible envelope M-V interaction curves in impact regime. Sectional forces are tracked with the help of Digital Image Correlation (DIC) supported with High-Speed Video (HSV). Impact tests have covered beam specimens with and without shear reinforcement to understand the different failure modes. Envelope interaction diagrams are proposed taking into account the curvature rate from the experiments, which allows considering the particular strain-rate conditions of the tests.