A Predictive Model for Local Damage Characteristic Dimensions of Reinforced Concrete Beams Subjected to Close-in Explosion

To address the lack of systematic quantitative prediction of local damage characteristics of reinforced concrete (RC) beams under close-in explosion, the Karagozian & Case concrete model is calibrated and validated. The tensile softening behavior and the influence of local characteristic length are modified, enabling the model to more accurately capture the damage evolution of concrete under blast loading. A finite element model of RC beams subjected to close-in explosion is established and validated against existing experimental results, demonstrating its effectiveness in reproducing the typical local failure modes as well as structural responses such as displacement and support reaction. Furthermore, the effects of charge aspect ratio, reinforcement ratio, and cross-sectional dimensions on the local damage patterns and characteristic dimensions of the reinforced concrete beams are systematically analyzed, revealing the governing mechanisms of these parameters on peeling-off length, spalling length, as well as crushing length and depth. On this basis, a predictive model for local damage characteristic dimensions is developed through the regression analysis of numerical results, and a correction factor is introduced to improve the prediction accuracy of spalling length. The findings indicate that the proposed model can accurately predict the local damage dimensions of RC beams subjected to close-in explosions, providing useful references for blast-resistant design and structural safety assessment.