Simulation On Dynamic Response Behavior Of Reinforced Concrete Slab With Variable Thickness Under Blast Load

Reinforced concrete is widely used in military facilities and civil engineering,with the escalation of worldwide terrorist attacks and regional armed conflicts,civilian buildings and military facilities have been attacked by explosive loads frequently.The civilian and military facilities buried deep underground and on the ground are threated seriously by the precision-guided and high-efficiency destructive weapons,the strike capability of this weapons has been improved continuously with the support of modern information technology.In order to improve the impact resistance of reinforced concrete protective structures,it is of great theoretical and practical significance to study the dynamic response of reinforced concrete structures under blast load.For the dynamic response of reinforced concrete slab of equal thickness under blast load,many scholars have carried out a lot of research and made many remarkable achievements,however,there are many reinforced concrete slab structures with variable thickness in practical engineering,such as slope slab,V groove slab and trapezoidal groove slab.Therefore,the ls-dyna finite element software will be used in this paper to focus on the numerical study of the dynamic response behavior of this kind of reinforced concrete slab structure with variable thickness under the action of explosion load,and then the influence of the geometric dimension of the groove on the anti-explosion performance of the slab was analyzed,so as to provide some reference for the design and safety evaluation of reinforced concrete protective structure.The main content of this paper are as follows:(1)Numerical research requires not only the establishment of a "reality" numerical calculation model and high-quality grid,but also the selection of a computational constitutive relationship that can accurately reflect the mechanical behavior of materials.This paper reviews relevant literature at home and abroad and investigat several kinds of dynamic constitutions of concrete such as the HJC model,RHT model and K&C model etc firstly.As a result,K&C model was selected as the computational constitutive model of concrete materials in this paper,and ls-dyna finite element software was used to conduct a single element test on K&C model,it was found that K&C model could well describe the confining pressure enhancement effect and strain rate enhancement effect of concrete material strength.(2)In order to verify the reliability of the numerical model,the numericalreproduction of the anti-explosion test of reinforced concrete slab was studied in this paper,and the failure morphology of the simulated target slab was compared with the experimental observation results.It was found that the coincidence between the two results was relatively high,indicating that the numerical model established in this paper has good rationality and reliability.(3)When the slope slab structure is subjected to blast impact load,the front is the slope surface,which is different from the flat face of detonation.To this purpose,the paper studied the slope form slab under explosion load response behavior,by comparing the anti-explosion performance of the slope slab with that of the slab under the same condition,it is found that the failure development process of the slope slab under explosion load is different from that of the slab,the destruction on the front of the slant slab is mainly concentrated in the thicker place on the right side and the area of destruction is smaller than that on the front of the slab,also the scabbing on the rear of the slant slab is smaller than that on the slab.(4)The anti-explosion performance of reinforced concrete slabs with variable thickness,such as v-groove and trapezoid groove,is simulated,the front is the side with groove.From the simulation results of failure pattern,Mises stress distribution on the back of the slab and stress distribution on the front of the plate,it can be found that V groove slab not only has a lighter failure degree,but also has a smaller stress peak than trapezoidal groove plate,this means that V groove slab is better than trapezoidal groove slab in anti-explosion performance.(5)The influence of inclined angle and the groove height of V groove on the whole anti-explosion performance of the slab was further studied.Through the comparative analysis of different angle and different slot high dynamic response behavior,study found that the failure range of the slab front and the transverse displacement in the middle span is the smallest when the inclined angle is 45°;In addition,when the groove height is small(the shape of the slabs is close to that of the slab,the anti-explosion performance of V groove slab is consistent with that of the slab;however,when the groove height is large,the slab is too thin in some positions,which may break easily;It was found that the anti-explosion effect was best when the ratio of groove height to total thickness was 1/3.