Research On Influence Of Offshore Ground Motion And Site Condition On Seismic Response Of Sea-crossing Isolated Bridges

Different from the land bridges,the natural condition of sea-crossing bridges is more complex.With the rapid growth of the number of sea-crossing bridges and the emergence of their earthquake damage,the seismic performance and seismic safety of sea-crossing bridges have been widely concerned.In this paper,the isolated continuous girder bridge commonly used in sea-crossing bridges is taken as the research object.In view of the influence of the offshore ground motion on the seismic response of sea-crossing isolated bridges.Based on the spectral analysis of the real strong earthquake records,the seismic response analysis of three-dimensional sea-crossing bridge and the wave analysis of fluid-soil-structure interaction,the influence of the onshore and offshore ground motion on the bridge response is compared.Also,taking the hong kong-zhuhai-macao bridge as an engineering example,the influence of site factors such as seawater layer and subsea soft-soil sediment layer on the bridge is further studied.It is found that the seismic response of the bridge structure is greater under the offshore ground motion,and there is a risk of the damage of isolation bearings.In addition,the seawater layer and the soft-soil overburden on the seabed have a magnifying effect on the seismic response of the sea-crossing isolated beam Bridges.Therefore,it cannot be ignored in the seismic analysis of sea-crossing isolation beam Bridges.The following will introduce the specific work content of this article.(1)This paper briefly introduces the development and main seismic damage of sea-crossing Bridges,and summarizes the research status of the characteristics for offshore ground motions and the seismic performance of sea-crossing bridges.(2)Based on the analysis of the onshore and offshore ground motion records collected in recent years,the correlation spectral characteristics of the onshore ground motion records with different site conditions and the offshore ground motion are compared,and the influence of local site conditions on the offshore ground motions is discussed.(3)Based on the seismic analysis method commonly used in engineering,the numerical model of three-dimensional sea-crossing isolated bridge is established.and7 groups of onshore and offshore ground motion records are selected to analyse the response of the key parts in the structure and the energy dissipation capacity of the isolation bearings,the response of the sea-crossing isolated bridges under onshore and offshore ground motion is compared.(4)Based on the theory of seismic wave and the use of artificial boundary,and combining the wave analysis program and the dynamic analysis software ADINA,a numerical model for considering seawater-soil-bridge coupling is established.The seismic influence of seawater layer and site condition on the sea-crossing isolated bridge is analyzed.