Study On Dynamic Response And Failure Mode Of Continuous Girder Bridge Under Blast Loading

In recent years,all kinds of explosions occurred frequently,which brought great loss of life and property.Bridge as a vital part of the transportation,carrying a very important transport task,the loss caused by the collapse of bridge will be immeasurable.The studies on explosion mainly limited in reinforced concrete members,but the studies of whole bridge blast-resistant performance are very few.The continuous girder bridge is the most widely used in practical engineering.Therefore,it is necessary to study the damage mechanism of continuous girder bridge under blast loading,which will provide a theoretical basis for the future blast-resistant design and damage assessment of bridge.In this paper,it's studied the propagation process of blast shock wave and the dynamic response and failure mode of reinforced concrete continuous girder bridge under blast loading by numerical simulation.The following research works have been carried out:(1)The propagation process of blast shock wave and the related parameters affecting the effect of shock wave are described in detail.The loading of air-blast is simulated by AUTODYN to analyze the influence of mesh size and TNT charge on simulation results,and then the numerical simulation results are compared with the results of empirical formula;(2)Base on the blast test of other researchers,an numerical simulation model of reinforced concrete girder under blast loading is established,and then the simulation result of failure mode of reinforced concrete girder is compared with it in the experiment,which can verifies the feasibility of numerical simulation;(3)Based on the actual project,the finite element model of reinforced concrete continuous girder bridge is established to study the dynamic response and failure mode of the bridge deeply.By changing the parameters such as the position of the explosive,the scale distance and the quantity of the explosive,the relationship between the failure mode of the bridge and parameters is studied on the upper explosion of girder.(4)When the explosion occurred at upper,inside and lower of the box girder,we analyze the action mechanism of the shock wave with the bridge and study the influence of explosion locations with box girder to the dynamic response and failure mode of the continuous girder bridge;(5)It's studied the blast shock wave propagation mechanism and the bridge damage after setting the protective components,and then compared it with not setting the protective components.Finally,it's analyzed the influence of the protective components to dynamic response and failure modes of the bridge.Research shows: the numerical simulation of reinforced concrete structure subjected to blast loading by AUTODYN software is feasible.For the blast-resistant performance,the middle span is the weakest position in reinforced concrete continuous girder bridge,which should be considered firstly in design of blast-resistant.When the quantity of the explosive or the distance of the explosives is same,the damage degree of the bridge is inversely proportional to the scale distance.When the explosion occurred inside the box girder,the damage to the bridge is the most serious.When the explosion occurred under the bridge,the damage to the bridge is the least.Setting protective components can effectively reduce the power of the explosion shock wave acting on the bridge,and reduce the damage degree of the bridge.These research results can be effective in prediction of continuous girder bridges subjected to explosion impact the extent of damage.Meanwhile they also can provide an important theoretical basis for the blast resistant design of continuous girder bridge,have very important application values in engineering.