Research On Bridge Damage Under The Coupling Effect Of Shock Wave And Fragment

As a transportation hub connecting two places,once the bridge is damaged,it will cause serious economic losses.The explosion will cause serious damage to the bridge and it is difficult to repair.In order to reduce the loss and harm caused by such events,it is necessary to study the damage of the bridge under the explosion load.In current studies,the impact of fragments on structures is usually ignored.However,some studies have found that,compared with the damage to structures caused by explosion shock wave alone,the structural damage under the coupling effect of shock wave and fragments is more serious.In view of this,this paper studies and evaluates the damage of the bridge under the coupling effect of shock wave and fragment.The main research contents of this paper are as follows:(1)The numerical model of shock wave and fragment under coupling action was established by ANSYS/LS-DYNA.Firstly,in order to ensure the accuracy of numerical simulation results within a reasonable calculation time,the calculated results of shock wave overpressure are compared with relevant empirical formulas to determine a reasonable mesh size.Secondly,a numerical model consistent with relevant experiments is established,and the accuracy of the numerical model is verified,which provides a basis for the subsequent work.(2)Through numerical simulation,increase the explosion condition of the warhead at different distances from the target,utilize the dynamic analysis of finite difference method and combine the results of numerical simulation,and establish the coupling effect model of shock wave and fragment,starting from the displacement of the structure generated by the coupling effect of shock wave and fragment.Furthermore,the impulse to the structure under the coupling action of shock wave and fragment is obtained through calculation,and the reason of the damage enhancement of the structure under the coupling action of shock wave and fragment is explained.Through the analysis of the coupling model results,it is found that the coupling effect between the shock wave and fragments after the explosion of warhead enhances the peak pressure on the surface of the structure after the explosion,and increases the total impulse on the surface of the structure.The increased impulse will cause more serious damage to the structure.For the subsequent damage assessment,the coupled model calculation can quickly obtain the pressure and impulse of the shock wave and fragment on the structure,providing more information for the damage assessment.(3)Through the equal damage curve establish the damage evaluation method of the bridge,and the damage grade of the bridge is evaluated according to the pressure and impulse calculated by the coupling effect model of shock wave and fragment.Then ANSYS/LS-DYNA was used to simulate the damage of T-beam bridge under the coupling effect of shock wave and fragment,and the damage of bridge under different equivalent warhead,different explosion distance and different explosion position was analyzed,and the damage of bridge was evaluated according to the established evaluation method.