Study On The Influence Of Slope Site On Seabed Seismic Characteristics And Seismic Response Of Sea-crossing Bridges

Although the construction of sea-crossing bridges is developing rapidly at present,the seismic design basically continues using the seismic research method of land bridges.The research on the influence of seabed ground motion,seabed topography and site conditions on the seismic response of sea-crossing bridges needs to be supplemented.Therefore,this paper takes slope sites commonly existing on the seabed as the major subjects,and systematically studies their influence on the seabed ground motion characteristics and the seismic response of sea-crossing isolated bridges,so as to provide reference for the accurate calculation of marine constructions such as seacrossing bridges.Firstly,this paper analyzes the related characteristics of ground motion of slope sites on the seabed,and analyzes the influence of slope,water depth,seismic incident angle and other factors on the characteristics of seabed ground motion.On this basis,the concept of critical slope is further proposed,and the range of adjacent slope of various seabed sites is given.In addition,taking the Hong Kong-ZhuhaiMacao non-navigable continuous girder bridge as an engineering example,combined with the submarine slope site fluctuation analysis method and the bridge multi-point seismic response analysis method,the seismic linkage input analysis method of crosssea bridge considering submarine topography is proposed,and the influence of submarine slope topography on the seismic response of cross-sea bridge is discussed.It is suggested that the terrain factor of slope site should be considered in marine engineering.The main finding of this study is as follows :(1)Based on the viscoelastic artificial boundary and wave analysis theory,the numerical simulation method of seabed ground motion is proposed.The results show that the seabed slope can significantly change the ground motion characteristics,and the accuracy of the results is verified by comparing with previous research results.(2)Comparing the ground motion results of different water depths and incident angles at the same slope site,it shows that water depth and incident angle have significant effects on the vertical response,but have different effects on the horizontal response.The water depth has little effect on the horizontal response,but the incident angle has obvious effect on the horizontal response.In addition,the ground motion characteristics under pulse input at different slope sites and the influence of different seawater depths on the ground motion characteristics of observation points at 5 % slope sites are studied.(3)The seabed site with smaller slope changes is set up and the motion characteristics are analyzed.The results show that the vertical ground response mutation slope is the critical slope when the P wave is vertically imported into the seabed site,and the influence of the depth of the sea water layer and the soil parameters of the cover layer on the critical slope of the site is studied.(4)The measured strong earthquake records are input into the bridge model by the multi-point input method,and the influence of slope site exceeding the critical slope on the seismic response of the sea-crossing bridge is analyzed.The results show that the slope site will amplify the response of the pier top and bottom,the relative displacement of the main beam and the bearing shear force,which greatly increases the damage risk of the sea-crossing bridge under the earthquake.It is suggested that the effect of terrain factors should be considered in seismic design of engineering.