Research On Mechanical Properties And Damage Of Concrete After Impact

With the acceleration of China’s urbanization process,the construction of urban transportation systems has entered a stage of rapid development.With the increase in the number of various interchanges and cross-line bridges in the city,the number of vehicle collision incidents has become more frequent.Bridges are very important transportation facilities.Operational safety is one of the factors affecting bridge structures.In the design stage,explosions,iMPacts,and collisions are usually considered as accidental loads.With the frequent occurrence of various traffic collision accidents,Certain economic losses and casualties will lead to the damage or collapse of the bridge structure.People are more and more concerned about the safety performance of bridge structures after being subjected to explosion,iMPact or collision.Therefore,after the bridge structure is subjected to explosion,iMPact or collision,whether the overall structure’s safety performance meets the requirements,whether the local structure’s safety performance meets the requirements,and whether the structure’s remaining bearing capacity can meet the requirements need to be effective and reasonable Analysis and evaluation.Concrete is currently the most commonly used material in bridge structures.Therefore,research on the dynamic mechanical response and damage degree of concrete after a collision is of great significance for assessing the safety performance and residual bearing capacity of the bridge.This paper is based on the ANSYS/LS-DYNA finite element calculation program,taking into account the mechanical characteristics such as contact nonlinearity,material nonlinearity and geometrical nonlinearity,and responds to the dynamic response,failure characteristics and damage degree of concrete under the iMPact of falling weight The numerical analysis is carried out.The main contents of this paper are as follows:(1)Using ANSYS/LS-DYNA software,a finite element model of a drop-crash concrete cylinder specimen was established,and a continuous pressure cap model(CSCM)was selected as the constitutive model of the concrete material under the iMPact load.At the same time,the finite element calculation results and experimental data are coMPared and analyzed.The results show that ANSYS/LS-DYNA software has good reliability for the numerical calculation of iMPact and collision problems.(2)A crash coupling model of a drop weight iMPacting a concrete test piece was established.The parameters of the drop weight,drop height,concrete axial compressive strength,and shape of the concrete were used to study the iMPact of the drop weight on the concrete test piece.Dynamic response and destruction characteristics.The results show that the weight of the drop hammer and the height of the drop are important factors for concrete failure.(3)The research on the residual strength of concrete after iMPact load was carried out.An evaluation method based on the cross-section damage factor was used to analyze the weight of the drop weight,the drop height,the compressive strength of the concrete axis and the shape of the concrete.Damage The residual strength of concrete specimens was calculated and analyzed by the method of "deformation".The results show that the drop weight,drop height,concrete axial compressive strength and concrete shape change will cause different degrees of damage to the concrete,and the residual strength of the concrete after iMPact can be effectively evaluated by the method of evaluating the damage factor of the section.Perform analysis.(4)The research on the mechanical properties and damage degree of reinforced concrete beams after being iMPacted by falling weights was carried out.The mechanical properties and damage levels of the reinforced concrete beams that were iMPacted were analyzed under different working conditions of falling height of falling weights.The damage degree of reinforced concrete beams was evaluated by establishing the formula of residual bearing capacity.