Investigation into vulnerability of reinforced concrete beams when exposed to short-duration severe dynamic loads

This investigation examines the dynamic behavior and residual lateral load capacity of reinforced concrete (RC) beams subjected to blast-induced loading conditions. A three-dimensional finite element representation of a typical RC beam was constructed using the explicit dynamics code LS-DYNA, incorporating detailed descriptions of material constitutive models, mesh generation strategies, and pressure application techniques. To ensure realistic simulation of high-rate response, both the concrete and steel material laws were modified to account for strain-rate sensitivity, which is known to significantly alter strength and deformation characteristics under impulsive loads. The predictive accuracy of the numerical model was established through systematic comparison against experimental data reported in the open literature, demonstrating good agreement in terms of deflection histories and failure patterns. Following successful validation, the calibrated model was employed in a comprehensive parametric study designed to explore how various design parameters influence blast resistance. These parameters included explosion characteristics (scaled distance), beam geometric properties (cross-sectional dimensions), material strengths (concrete compressive grade and steel yield grade), and longitudinal reinforcement ratios. Furthermore, the behavior of critical cross-sections at locations of maximum distress was analyzed in detail to quantify damage progression and evaluate post-blast safety margins. Damage levels were classified according to a proposed cross-sectional damage index, enabling consistent assessment of structural integrity under severe dynamic events. While the study focuses on isolated beam elements, the findings offer direct relevance to the vulnerability assessment and blast-resistant design of concrete bridge structures, particularly for critical girders and deck components exposed to accidental or intentional explosions. The proposed damage index provides a practical tool for evaluating the post-blast serviceability of bridge spans and informing decisions regarding traffic reopening or structural repair. The findings provide practical guidance for the blast-resistant design and vulnerability assessment of RC beams in buildings and infrastructure exposed to accidental or intentional explosions.