The Dynamic Response And Failure Mode Of Overpass Bridge Under Explosion

City overpass is widely used in highway and urban rapid road traffic in the network.Influence by the larger span,traversing the more sections, geographical environment and the traffic route,city overpass generally consists of straight bridge and curved bridge.And city overpass affected by various external factors in the process of operation,so explosion by the reasons for accidents, terrorist attacks and the war caused can not be ignored.It is because of the complexity of irregular,city overpasses suffer bomb attacks is more vulnerable. When the explosion occurres,severe explosion may cause damages of local reinforced concrete, beam falling and bridge continuity collapse.Simply supported beam bridge and curved bridge is established respectively.Building up the finite element model,comprehensive study of dynamic response and destruct mode under explosion load is carried out with explicit dynamic contact search algorithm.Research contents and research achievements in this paper include the following aspects:For single span simple supported T beam bridge as the engineering background,then1000kg explosive is placed near the left beam end.In the process of explosion, the only cause local girder damage, bridge did not cause the overall collapse destroyed.The extent of the damage bridge components blasting area around the source point is more than slightly far range in the local area around the point of explosion source.Far away from the blast damage of bridge components are very small, and the damage position has no direct relation with dynamite.The beam body near the explosion source draws and while the main beam end significant upwards by blast and impact loads.Focus on simply supported T beam bridge under blast loading response and collapse process after placed2000kg explosive in the left end beam bridge between double pier,and then the bridge overall collapse.Its the damage form of successively performance in the collapse process as followingrleft pier column bottom section element first failure,the beam end close to the blast point falls down,the beam end away from the explosion point from the bent cap slide,the beam end near the explosion point hit the ground,the beam near the midspan section in the break,the beam end away from the explosion point break right pier column and so on.Therefore, the pier column is a key component for blast resistant design of simply supported beam bridge.It can prevent explosion collapsed bridge to a certain degree that take effective measures of protection on the pier column.Finite element calculation model of assembled three span curved continuous rigid frame bridge is established and applying200kg explosive of blast load in medial, lateral of external bridge and above the single column pier respectively.Research shows that explosion effect significantly intensified bending-torsional coupling degree of the curved girder bridge of main beam.And the explosion caused the local damage, and not caused by the collapse of bridges.Away from the explosion source location of pier area of the extent of damage has nothing to do with the location of the explosive.All showed the highest degree of single column pier damage and the extent of damage of lateral pier of double column piers is higher than that in the inner side of pier.Placing200kg explosive in curved beam bridges with single column pier feet by Fluid-Solid Coupling method and Three-Stage Method show the process of explosion collapsed.It makes single column pier bottom element instantaneous failure through detonation and the single column pier top beam body gradually falling under gravity.The right end beam support plays a role of the constraint by stop the girder falling and the bottom of the beam element around spring failure.The right end support losing restraint makes the right end main beam continue to fall.Then the girder cantilever root break. Finally,the beam body reverses and falls to the curve of the lateral.Therefore, it should that strengthen the connection constraint component design such as support, and the single column pier of curved girder bridge reinforcement protective measures in the explosion of the curved girder bridge collapse resistance design.