SUMMARYReinforced concrete is a composite structural material which has been the subject of extensive research since it was first used. When considering the rational properties, the research has mainly centred on the behaviour of the concrete, that of the reinforcing steel and the interaction between the steel and the surrounding concrete subject to static loading. The behaviour of reinforced concrete, and, in particular, that of the concrete itself when subject to dynamic loading has been less thoroughly studied.This paper proposes a material model for the concrete which includes the effect of high strain rate upon both the stiffness of the material and upon the crushing strength. It proposes expressions for the yield and failure surfaces of the concrete which account for the effects of high strain rate and then incorporates this material model into an existing finite element program to compare with a series of test results. The paper illustrates that this improved material model can now produce a displacement/time history for reinforced concrete elements which is very close to that observed in tests on elements which are far outside the elastic range.KEY WORDS reinforced concrete; dynamic analysis; strain rate effect: matend modelling

The main objective of the current research work is to investigate the dynamic response of reinforced concrete (RC) slab protected by a composed layer of aluminum foam panel and steel plate. The RC slab and the protection layer were subjected to blast loading. A parametric study was conducted in which a series of numerical simulations of protected and unprotected RC slabs was performed using hydro-code software (i.e. AUTODYN 3D). A set of published experimental tests was used to validate the numerical models proposed. The models were simulated as protected and unprotected RC slabs subjected to different blast loads. In the numerical simulations, the dynamic behavior of reinforced concrete and aluminum foam materials as porous materials were defined utilizing different Equations of State (EOS) and strength models. Time-dependent results of the response of the RC slabs subjected to the blast loads were obtained. The computed results were then utilized to study the efficiency of aluminum foam and steel plate layer to maintain the maximum deflection of the RC slab within its elastic limit.

Evolution of the ballistic threat has taken place, principally, in the contexts of general war, terrorism and crime. The threat has been developed to cause injury or damage to personal, land vehicles, ships, aircraft and structures. Inert projectiles will cause only localized damage to structural targets and therefore normally constitute a less potent threat to the survival of the structure than rounds which have high explosive contents. This paper describes the spectrum of ballistic threats on armoured structures. The results from FEM simulations of steel projectile penetrating sandwich honeycomb armours are discussed. The simulations are performed in 3D AUTODYN software [1]. Finally, the armours with composite systems and different materials subjected to blast loads will be discussed. The results show that the ceramic-faced armours cause reduction in projectile exit velocity by about 29.4 % and 39.6% for ceramic thicknesses 10 mm and 20 mm respectively. Also the result indicate that the honeycomb reduce the displacement due to blast loads by about 77.24%, only with 3.586 % increasing in the total weight of the armours.

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