Dynamic Response Prediction of RC Structural Components Subjected to Combined Blast and Fragment Impact

The paper presents a methodology for enumerating the dynamic response of one-way reinforced concrete (RC) structural elements subjected to combined blast and fragment loading, a scenario commonly associated with the detonation of cased explosive charges. The proposed methodology is motivated by the relatively few studies published in this area and the simplified design procedures that are currently used for addressing this problem. The formulated framework, in addition to the consideration of the blast and the fragment loading, also accounts for the damage incurred by the member due to the localized penetration caused by the impacting fragments. The fragment-induced damage is accounted for by considering a member having a reduced cross-sectional depth, i.e., a damaged member. Material nonlinearity and the strain rate-sensitive aspects of both concrete and steel are also considered. The dynamic structural response of the member was quantified by idealizing the member as an equivalent single-degree-of-freedom system. Finite-element (FE) simulations were conducted by the authors for assessing the efficacy of the adopted formulations. On the basis of the comparative assessment, the results of the FE simulations were found to match relatively well with the results of the proposed approach (relative difference being in the range of 8.95%-12.67%). Additionally, the peak displacements for the cased explosive charges were noted to increase by approximately 31%-123% compared to bare (uncased) explosive charges of similar charge weights. While this observation underlines the severity of cased explosive charges, it also qualitatively highlights the damaging propensity of the striking fragments, a component that generally is not exclusively considered for design purposes. (C) 2021 American Society of Civil Engineers.