Effect of seismic isolation on random seismic response of High-Speed railway bridge based on probability density evolution method

In order to evaluate the effect of seismic isolation on random seismic response characteristics of a track-bridge system, in this paper, a three-dimensional detailed nonlinear dynamic model consists of rail, CRTS II slab ballastless track, high-speed railway simple supported bridges, isolated bearings, piers, pile foundations from top to bottom, is established by OpenSEES. The stochastic process of ground motion constructed by the random harmonic function is taking as random excitation, and the probability density evolution method (PDEM) is applied to investigate and analyze the system from the random perspective. On this basis, the influence of FPB bearing and the different FPB parameters (such as equivalent radius) on the random seismic response of the track-bridge system is studied. Thereby, aplenty probabilistic information (probability density evolution function, mean value and standard deviation) can be gained of seismic response of isolated bridges with different isolation parameters and non-isolated bridges of the high-speed railway track-bridge system under the excitation of random earthquakes by case study. Through the comparison of random seismic responses of non-isolated bridge and isolated bridges with different parameters under random ground motions, the favorable and unfavorable effects of seismic isolation for high-speed railway bridges are explored and demonstrated from a random point of view. The comparison of the random seismic response under different cases are discussed and significant outcomes are drawn. Results show that: The use of isolation bearing can reduce the response of track structure and pier, but meanwhile, increase the response of bearings. The change of the equivalent radius of the isolation bearing has no obvious influence on the random response of the pier and the track structure, but will to some extent bring the change of the bearing response. The results can be used for the seismic design and maintenance of the railway high-speed bridge.