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Reinforced concrete (RC) structural members subjected to blast loading behave differently as compared to the same subjected to quasi-static loading. Numerical studies are conducted to study the influence of weights and positions of explosive charges, locations, widths and depths of initial cracks, and longitudinal reinforcement ratios on the dynamic behavior of simply supported RC beam with initial cracks (pre-cracked RC beam) under air blast loading. Results show that, compared with the perfect beams, the pre-cracked RC beams present themselves with an increase in the maximum deflection of mid-span, the maximum vertical velocity of mid-span node, effective stresses of concrete in compressive zone of the pre-cracked RC beam, and axial stresses of longitudinal reinforcement in tensile zone of the pre-cracked RC beam. Due to stress concentration of pre-cracked sections under air blast loading, the presence of initial cracks at the mid-span (or the end) of the pre-cracked RC beam could cause the failure of the pre-cracked RC beam prematurely at the cracked sections and where the blast loading begin to be loaded. Moreover, a crack on the surface of compression zone of the pre-cracked RC beam has a larger influence than that on the surface of tensile zone. The damage generated by blast loading effects is limited to a local area, and the dynamic behavior of the pre-cracked RC beam is not sensitive to the width and depth of initial cracks to some extent.

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