Dynamic Response And Damage Deformation Of Preloaded Reinforced Concrete Slabs Under Impact Loading

Reinforced concrete structure is widely used in all kinds of buildings because of its good stability,durability,fire resistance,convenience of materials and low construction cost.Once the reinforced concrete structure is subjected to the impact load during the construction and use,it may lead to the damage of the structure and even lose the bearing capacity and cannot continue to work.Therefore,it is of great significance to carry out the research on the dynamic performance of the reinforced concrete structure under the impact load.In this paper,the static load of the reinforced concrete slab is taken as the pre-loading load,and the finite element software ABAQUS is used to establish the model of the pre-loading reinforced concrete slab,and the dynamic response,impact response mode and damage of the pre-loading reinforced concrete slab under impact are studied.The main research contents are as follows:（1）The finite element model of pre-loaded reinforced concrete slab under impact load is established and verified by the impact test of drop weight.Considering the strain rate effect of reinforcement and concrete under impact loading,the plastic damage model（CDP model）was adopted for concrete,and damage factors were introduced into the CDP model to define the damage evolution behavior of concrete.The reinforcement model consisted of five stages,namely,elastic section,elastoplastic section,plastic section,strengthening section and secondary plastic flow section.The effectiveness of the finite element simulation results is verified by comparing the impact test of the falling weight of reinforced concrete slab with the finite element simulation results by using the hourglass energy control and the existing ones.（2）The dynamic response analysis of preloaded reinforced concrete slab under impact load is carried out.A reinforced concrete slab model with different parameter combinations was established to analyze the effects of preloading,impact mass,impact velocity and reinforcement ratio on the system energy,impact force and vertical displacement of the reinforced concrete slab under impact.The analysis results show that the system energy,impact force and vertical displacement of the plate center are most affected by impact velocity.When the impact velocity is 2.5m/s～10m/s,the variation range of system energy is about 106.14%～132.18%with the change of impact velocity.The impact force varied from 52.21%to 177.04%.The central vertical displacement of reinforced concrete slabs increases by about 309.01%～314.68%.When the impact velocity is less than 10 m/s,the maximum displacement of the plate center increases by 22 times with the increase of the impact velocity by 2 times.（3）The impact response model of reinforced concrete slabs under impact load is studied.Reinforced concrete plate after the shock load,according to the damage of plate and deformation divided three types of shock response model,through the regression analysis of fitting of the lower shock load center deflection calculation formula,based on the maximal displacement criterion is given three shock response pattern corresponding to the center deflection and calculation span ratio range,when scratching across more than?δ/l₀≤0.4% or less of a shock response patterns,scratching across than 0.4%<δ/l₀≤0.95%or less for shock response mode 2,scratching across than?δ/l₀>0.95% when the corresponding response patterns.（4）The damage and deformation of reinforced concrete slab subjected to impact load under different parameter combinations are analyzed.The results show that the impact mass has the greatest influence on the damage and deformation of the plate under impact.When the impact mass is in the range of 150kg～250kg,the change of deformation area in the damaged area caused by the impact mass is 0.18%-0.32%.When the bearing capacity of the plate is subjected to impact load,the deformation area of the plate is in the area of 327mm～345mm with the center of the plate as the center of the circle.When the plate is damaged and fails under the impact effect,the deformation area of the plate is in the area of 550mm～625mm.