Study On Seismic Response And Radial Limit Of Curved Bridge Under Bidirectional Earthquake

The curved bridge can overcome the terrain,the geomorphic constraints,and have a beautiful overall line,which is widely used in mountain bridge,urban overpass and landscape bridge.Although scholars at home and abroad have done a lot of research on the response characteristics of curved bridges under earthquake,but in many large earthquakes,there are still very serious disasters in curved bridge.Therefore,it is of great significance to study the characteristics of seismic response of curved bridge under horizontal and bidirectional earthquake,the limiting measures and the application of isolation technology.The main contents of this paper are as follows:(1)To collect the relevant information of common seismic damage of curved bridge s in previous strong earthquakes at home and abroad,and summarize the background and present situation of seismic response and seismic absorption of curved bridge.(2)The advantages and disadvantages of nonlinear time-history analysis,the calculation steps and the necessity of using nonlinear time-history analysis for curved bridges are summarized.Then establish the finite element model of curved bridge with support nonlinearity and nonlinear connection(isolation element).(3)Referring to the method of selecting horizontal and bidirectional seismic waves in previous studies,several strong earthquake records consistent with the assumed site category were selected from the database of the Pacific Seismological Research Center of the United States.It is also ensured that the“SRSS spectrum”of the two horizontal components recorded by strong earthquakes is fitted well with the design response spectrum of the code.(4)The response characteristics of curved bridge under multi-dimensional earthquake excitation are studied,and the difference between the response of curved bridge under horizontal unidirectional and horizontal bidirectional seismic waves at different excitation angles is compared and analyzed.Two methods for calculating the most unfavorable excitation angle of curved bridge under horizontal and bidirectional seismic wave excitation are discussed,and the relationship between the most unfavorable excitation angle and curvature radius is found out.(5)The response of the curved bridge considering radial limit of concrete block is analyzed,and the influence of seismic wave excitation method and angle,block stiffness,initial clearance,site class and elastic-plastic of pier column on the radial impact of the curved bridge are summarized.Some conclusions are drawn in favor of engineering application.(6)Viscoelastic dampers are added to the model of curved bridge considering concrete block,and the optimum values of the key parameters,such as shear stiffness,damping coefficient and damping index,are selected through parameter analysis.Compared with the curved bridge model with concrete block only,this paper provides a reference for seismic design of curved bridge.(7)Replacing the traditional concrete block with X shape elastic-plastic steel block.The influence of initial stiffness,yield strength and yield stiffness ratio of steel block on the application effect of steel block on curved bridge is studied,and the optimum value of key parameters of steel retaining block is selected.The difference of seismic response between X shape elastoplastic block model and concrete block model is compared and analyzed.