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a b s t r a c tA field measurement of ground vibration was performed on the Beijing À Shanghai high-speed railway in China. In this paper, the experimental results of vertical ground vibration accelerations induced by very high speed trains running over a non-ballasted track on embankment with speeds from 300 to 410 km/h are reported and analyzed in detail for the first time. Characteristics of ground vibration accelerations in both time and frequency domains are analyzed based on the test data. It is shown that the periodic exciting action of high-speed train bogies can be identified in time histories of vertical accelerations of the ground within the range of 50 m from the track centerline. The first dominant sensitive frequency of the ground vibration acceleration results from the wheelbase of the bogie, and the center distance of two neighboring cars plays an important role in the significant frequencies of the ground vibration acceleration. Variations of time-response peak value and frequency-weighted vertical acceleration level of ground vibration in relation with train speed as well as the distance from the track centerline are also investigated. Results show that the time-domain peak value of ground vibration acceleration exhibits an approximately linear upward tendency with the increase of train speed. With the increasing distance from the track centerline, the frequency-weighted vertical acceleration level of the ground vibration attenuates more slowly than the time-domain peak value of the ground vibration acceleration does. Severe impact of high-speed railway ground vibration on human body comfort on the ground occurs at the speed of 380-400 km/h. The results given in the paper are also valuable for validating the numerical prediction of train induced ground vibrations.

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This paper describes an experimental program conducted to investigate the effects of fluid-structure interaction on the modal dynamic response of three reduced-scale bridge pile foundations submerged partially or totally in water. The vibration periods of the specimens are measured for the two lateral modes and first torsional mode using ambient and forced-vibration tests. The results are presented and discussed as a function of surrounding water levels and the number and geometrical patterns of the piles. Three-dimensional (3D) finite element models of the tested specimens surrounded by different water levels are built and the results are successfully validated against the obtained experimental data. The built numerical models are used to compute 3D modal hydrodynamic pressures. A systematic analysis of the period ratios and 3D hydrodynamic loads is presented to characterize the effects of pile cap, water height and the number and geometrical pattern of the piles on dynamic response. The experimental and numerical results of this research allow a better understanding of the complex dynamically-induced fluid-structure interaction effects in the response of deep water bridge pile foundations.