Study On Shock Isolation And Reduction Of Bridge Structure Subjected To Explosive Loading In The Underground Tunnel

The explosion in the underground tunnel may cause the destruction of the tunnellining and maybe affect the structures underground or on the surface of the earth, andit could also cause obvious vibration and even local failure of structures. In this paper,the shock isolation and reduction of two types of bridge structures, such as thecontinuous girder bridge and the cable-stayed bridge, subjected to explosive loadingin the underground tunnel is investigated numerically. The main research work andconclusions are drawn as follows:(1) ANSYS/LS-DYNA software is used to simulate exploding process in theunderground tunnel and the overpressure history on the inner surface of tunnel isobtained; The three-dimensional tunnel-soil-bridge-water coupling model isestablished by using the ANSYS/LS-DYNAsoftware and also the constitutive modelsof soil, concrete and water, applicable to blast load, are established and thesemi-infinite soil foundation is simulated byusing non-reflecting boundary. The shockisolation effects of two types of bridge structures, such as the continuous girder bridgeand the cable-stayed bridge, are compared in different situations including setting therubber bearing, setting the rubber bearing and viscous dampers jointly andconsidering different water depth.(2) When bridge is subjected to explosive loading in an adjacent undergroundtunnel, the rubber bearing can make full use of its characteristic of small shearstiffness to increase the ductility and extend the vibrating period of the bridge, andrubber bearing is advantageous to the seismic isolation of bridge structures. The waterunder bridge can reduce the transverse direction response of continuous girder bridgeand the cable-stayed bridge, but it can increase the vertical response and the deckstress of continuous girder bridge. The response of continuous girder bridge isincreased with the water depth. That is to say the response is maximum during flood,ordinary during constant level and minimum during drought. The water under bridgecan reduce the deck stress of cable-stayed bridge, but there is no obvious law in therespect of the vertical response.(3) Viscous dampers arranged on the transverse direction not only cansignificantly reduce the transverse direction response of continuous girder bridge andcable-stayed bridge but also can lower effective stress of some part of deck in the continuous girder bridge. Besides, it also has a definite effect on reducing the verticalresponse of cable-stayed bridge, but it has no effect on reducing the vertical responseof continuous girder bridge. Viscous dampers arranged on the longitudinal directioncan lower the longitudinal direction response of continuous girder bridge andcable-stayed bridge, but the effect varies with position. At the same time, it can reducethe vertical response of bridges as well as the effective stress of the deck, which has asignificant effect on seismic isolation.