Study On The Sensitivity Of Random Dynamic Response Of Seismic-isolated Bridges Under Non-Uniform Ground Motion Excitation

With the progress of bridge engineering in China,the construction of new bridges in remote mountainous areas and coastal areas has become an inevitable trend.These areas usually have complex geological conditions and high seismic intensity,which require higher seismic performance of bridge structures.As an effective means to improve the seismic capability of structures,the seismic isolation technology has been applied successfully in building structures.The construction and planning of seismic-isolated bridges in China still has massive potential.Therefore,within this background,how to further develop and improve the theory of isolation bridge analysis and design to accurately evaluate the seismic performance is one of the important scientific problems that requires further in-depth study.The spatial variability of ground motion should be considered in seismic response analysis of multi/large-span structures,whether isolated or not.The corresponding power spectrum and cross-power spectrum parametric models of non-uniform ground motion are established.The sensitivity of the statistics of bearing displacement,pier displacement and other important response quantities are analyzed.The main work of this thesis is described as follows:(1)By reading a large number of literatures and collecting data,this paper summarizes the state-of-the-art of bridge stochastic response under non-uniform excitations,and gives the background and purpose of the research.(2)The theory of random vibration of structures is introduced in detail,including impulse response function,frequency response function,power spectral density function,etc.The formulas of the correlation function and the power spectral density function of the random response of the linear single-degree-of-freedom system under the action of random earthquake are derived.The stochastic ground motion model is introduced,which is represented by the power spectrum model.Finally,the spatial variation effect model of ground motion is introduced.(3)The displacement input and acceleration input method under non-uniform excitation are introduced,and then the dynamic analysis method for the equation of motion under non-uniform excitation is discussed.The response spectrum theory under non-uniform excitation is introduced.Finally,the sensitivity analysis formula of for site effect is derived,and an example is given to show that when the frequency of the supporting soil is close to that of the structure,the response of the structure increases rapidly.The displacement response of bridge piers is larger when the site conditions vary significantly.(4)Introduce the development process of finite element and the finite element analysis process,then program the vibration isolation bridge model,and finally study the sensitivity of spatial variability of ground motion to the random dynamic response of vibration isolation bridge structure.