Study On Failure Behavior Of Reinforced Concrete Beam Its Influencing Factors Under Impact Loads

Reinforcement concrete(RC)is the most common building material which has been widely used not only in the civilian areas,but also in protective engineering and military installations/facilities.These RC structures inevitably suffer from the blast or impact loading.Therefore,experimental studies and theoretical analysis on RC members(such as beams,columns,plates.)subjected to impact or blast loading have been paid widespread attention.In this paper,the response characteristics of RC beams under drop weight impact were studied experimentally and numerically,the main contents include the following two parts:(1)A drop weight impact experiment and the finite element(FE)analysis are conducted by the samples of plain concrete beam and light RC beam without stirrups,the results show that: the failure pattern of light RC beam is relate to the longitudinal reinforcement ratio and loading rate,which vary from predominantly flexure to shear failure with the increase impact velocity,and the punching shear will be the predominate failure pattern for beams under high speed impact(V> 10 m / s in this paper).Furthermore,the critical velocity of shear failure mode transformation will increase with increasing longitudinal reinforcement ratio,and the variation tendency of the failure behavior and response of RC beam simulated by FE model is in good agreement with the experimental phenomena.(2)A numerical simulation is established by FE code to analyse the dynamic behavior of the standard RC beam(with stirrups)under impact loading based on the experimental data.Two boundary conditions including simply supported and fixed ends are also investigated,main attentions are paid to the effect of boundary condition on failure model and the impact behavior of RC beam.The results are as follows: the flexural failure is predominate failure pattern of the standard RC beam at low-velocity impact and it would transform to the shear failure with the increasing loading rate,and the larger the impact velocity,the more compact the damage.Additionally,the boundary condition significantly affects failure of the beams at low-velocity impact(V<4.85 m /s in this paper),furthermore,the damage of fixed-end beam is more serious than that of the simply-supported beam,and the diagonal tension failure would more likely to occur at the fixed ends.However,the boundary conditions is marginal on the failure mode of the beams while impact speed is high(V> 9.7m / s in this paper).