Simulation Study Of Effect Of Steel Bar On The Anti-penetration Property Of Concrete Target

Concrete and steel are the main raw materials for infrastructure construction,and widely used not only in the civil field,but also in the military field.In the military,such as underground command work,weapons and ammunition depot and oil storehouse and other important military projects.In the civil field,concrete is used to place safety shells for the construction of nuclear facilities,large bridges and some super high-rise buildings.When these important buildings are the target of attack,how to effectively destroy the target and how to effectively play a protective function have becomes a major concern.The existing research results are mainly focused on the penetration of projectiles into plain concrete targets.In fact,the actual protection works are usually reinforced concrete structures.Relative to plain concrete,the resistance of the projectile in the process of penetration should be determined by the joint of concrete and steel.The reinforcement factor will also seriously affect the final result of projectile penetration.Therefore,the research on the influence of reinforcement factors on the penetration resistance of concrete targets has become the focus.This paper uses the separation modeling method to establish the target plate model of reinforced concrete.The LS-DYNA finite element explicit nonlinear dynamic analysis software is used to simulate the penetration of rigid projectiles into reinforced concrete targets,considering the influence of steel factors on the penetration resistance of concrete.The main contents of this paper are as follows:(1)The formation process of each response area of plain concrete during penetration is introduced.According to the characteristics of each response area,based on the two threshold value of concrete ultimate compressive strain and ultimate tensile strain,the cavity expansion response regions of concrete target are identified and the size of each concrete response region in penetration process is obtained.The effect of penetration velocity on the crushed and cracked zone is analyzed.The relationship between the boundary expansion velocity of crushed /cracked regions and the penetration velocity are discussed.The results indicate that with increasing the initial impacting velocity,the interface velocities of crushed/cracked regions and the radius of crushed region are increased,but the radius of cracked region is decreased.At last,the crackedregion may disappear when the penetration velocity achieves a certain critical value.(2)First of all,on the basis of the recognition and division method of each response zone of concrete,the size of each response zone in the process of penetration of reinforced concrete is given.And compared with the plain concrete,the influence of the steel on the response zone is obtained,in order to deduce the restraining effect of the steel bar on the concrete.Then the paper discusses the effect of steel ratio on the response region of concrete.In the end,the effect of the restraining effect of steel bar on the penetration resistance of concrete is given.The results show that the steel have a significant effect on the response regions of concrete,and the existence of steel inhibits the expansion of the response regions.At the same penetration velocity,the size of the crushed and cracked zone and the corresponding boundary expansion velocity decrease as the reinforcement ratio increases,that reinforced concrete Circumferential constraint reduces crushed/cracked zone of concrete,inhibiting the expansion speed of each boundary,thereby reducing the damage area of concrete.