Study On Stochastic Seismic Response And Reliability Methods For Isolated And Energy-dissipation Bridges

Seismic ground motion is a typical random process.With the development of bridge seismic design technology,it has become necessary to carry out bridge seismic design research using random vibration theory.Due to the randomness of ground motion,and the hysteretic constitutive behavior of isolated bearings and viscous dampers,the seismic response of isolated and energy-dissipation bridges is a typical local nonlinear random vibration problem.Although the nonlinear random vibration theory has been developed for more than 50 years with various important progresses,it is still far from mature.Particularly,the nonlinear random seismic response analysis methods of isolated and energy-dissipation bridges have rarely been studied.At present,the seismic design method of bridges is based on the theory of elastic response spectrum.Due to the convenience of linear random vibration theory based power spectrum method,power spectrum method is becoming an alternative choice for seismic design of bridges.If the hysteretic constitutive model of isolation bearings or viscous dampers can be linearized,a power spectrum method of isolated or energy-dissipation bridges can be established.Using the power spectrum method,engineers can easily design the types of isolated bearings and viscous dampers.Especially for the widely-used regular isolated bridge,it is meaningful to develop a simplified analysis method.The dissertation is focused on the establishment of random seismic response analysis methods for isolated and energy-dissipation bridges within the framework of random vibration.The study considers the randomness present within the ground motion as well as within the bridge structure.The dynamic reliability of isolated and energy-dissipation bridges is also studied.The main work of the dissertation is as follows:(1)The research progress on random vibration analysis methods,dynamic reliability analysis method,and random seismic response analysis and reliability analysis methods for isolated bridges or energy-dissipation bridges are systematically reviewed.(2)Aiming at the local nonlinear analysis of isolated and energy-dissipation bridges,based on structural dynamics and finite element theory,the equations of motion for isolated and energy-dissipation bridges subjected to multi-support seismic excitations are established.After separating the local nonlinear term in the equations of motion,and using a precise time-integration method,namely the Rangkutta method,in conjunction with a random simulation technique,a nonlinear random vibration analysis method for isolated and energy-dissipation bridges under multi-support seismic excitation are established.(3)To facilitate convenient isolated bearings and viscous dampers design for bridges subjected to multi-support seismic excitations,using complex mode superposition method and existing equivalent linearization methods for isolated bearings and viscous dampers,the power spectrum methods of isolated and energy-dissipation bridges are established.(4)Regular isolated bridges are widely used in engineering practice,the response under earthquake action is typically controlled by the first mode.To further simplify the computation process,regular isolated bridges can be simplified to a single column and mass system.Firstly,according to the restoring force model specified in the seismic design,the constitutive model of the isolated bearing and its corresponding pier/column is described as a bilinear model.Secondly,based on the stochastic equivalent linearization theory,the bilinear model is equivalent to a single-degree-of-freedom(SDOF)linear structure.Finally,based on the power spectral theory,the random seismic response of the SDOF linear structure is solved.(5)The purpose of the random seismic response analysis of isolated and energy-dissipation bridges is to evaluate the seismic reliability.Based on previous random seismic response analysis method for isolated and energy-dissipation bridges,and combining seismic reliability analysis method with Subset Simulation using Hamiltonian Monte Carlo method,the seismic reliability methods for isolated and energy-dissipation bridges are established.In the dissertation,according to the seismic fortification criterion in current seismic specification,using results of seismic hazard analysis,the occurrence probability of earthquake action E1 and E2 in the current seismic specification is analyzed.On this basis,the reliability analysis methods for isolated and energy-dissipation bridges in design reference period are established.(6)Due to the uncertainty in bridge construction,the randomness in the physical and geometric parameters of bridge structures is inevitable.In the dissertation,using the property of mutual independence between random excitation and random structural parameters,based on the law of total probability,number theory and concept of the importance ring,the random earthquake response analysis and reliability analysis method for isolated and energy-dissipation bridges are established.