BLAST LOADING ON REINFORCED CEMENT CONCRETE BARRIER

Abstract

Blast loading on structures is an extreme event in which pressure pulse with overpressure many times above atmospheric and very high specific impulse impinges on surfaces of the structure. The effects of blast wave on RCC structures constitute damage in the form of cracks, spalling, scabbing and excessive deformation. The material behaviour in this stress range is essentially non-linear and affected by high strain rates. In this work, numerical studies on Abaqus/explicit were performed to study effect of blast waves on 2 way simply supported RCC slab for different combinations of charge weight and standoff distances. The damage to the slab for different cases was observed. It was concluded that damage increases more rapidly with decreasing standoff distances as compared to increasing charge weight. The conventional blast resistant design of structure constitutes idealising the structure as a single DOF system and blast loads as impulse loads. The design objective is to make the structure stiff and ductile enough to sustain a predefined deformation and damage level based on protection category. In the presented work, design of cantilever and fixed blast barrier for protection categories type 1 and type 2 for a specified blast load has been presented. The effect of presence of sacrificial cladding of cellular foam such as aluminium foam has shown promising results in protecting structures against effect of blast loads. Numerical studies to compare the performance of blast barriers with and without sacrificial cladding is undertaken. The data for material models used for modelling the behaviour of concrete, steel and aluminium foam namely concrete damaged plasticity, Johnson cook hardening and crushable foam model respectively were taken from literature and validated by replicating experimental programs. The numerical studies to compare the performance of blast barriers with and without foam cladding showed that foam cladding significantly reduced concrete damage and deformation. Foam claddings are effective in reducing damage by global response Page | iv reduction and attenuation of stress waves in solids. It was found that stiffer and lighter blast barriers are better suited for global response reduction using sacrificial foam. Numerical studies were performed to compare the efficacy of sacrificial foams of two different thicknesses and of two different densities. It was concluded that increasing thickness of foam cladding beyond minimum design thickness is not beneficial and that foam of lower density is better suited for stress wave attenuation