Effect of Combined Blast and Fragment Loading on RC Wall and Its Mitigation Using Composite Sections

The damages incurred in RC walls subjected to combined loading of blast and fragment as a result of a cased-charge detonation are studied here using the finite-element (FE) analysis method. A series of FE analyses were performed to estimate the intricate effects of cased explosive charges on severe crushing of concrete leading to spalling, penetration, or even scabbing and perforation in concrete. An increase in fragment penetration and perforation was noted under combined loading of blast and fragment compared with fragment loading alone, which highlights its severity. Subsequently, the response of RC walls of different thicknesses and concrete compressive strengths under different cased loadings and fragment shapes was also studied. Results showed that the response of the RC wall is considerably affected by charge weight, casing weight, concrete compressive strength, wall thickness, and fragment shape. The spherical end fragment penetration under combined loading of blast and fragment was noted to increase by 5.4%-23.1% compared with similar fragment loading alone, considering different concrete strengths. Moreover, based on the numerical study, the empirical relation of fragment penetration is modified and proposed to include the effect of explosive charge and casing weight. The measures to prevent excessive scabbing and concrete perforation using composite sections of concrete-steel and concrete-sand-steel, respectively, are also presented. This study emphasizes the importance of considering combined blast and fragment loading of protective structures and its mitigation using composite sections.