Jian Song

Sliding Displacement of Flexible Earth Slopes Subject to Near-Fault Ground Motions

AbstractA fully coupled simplified method that incorporates soil nonlinearity is used to conduct sliding-block analysis of slopes subjected to near-fault pulse-like and nonpulse-like ground motions. The effects of the ground motion pulse on the computed sliding displacements are investigated, and the efficiency of various ground motion intensity measures for predicting the sliding displacement of slopes is evaluated. It is shown that the slope is expected to have larger displacements over shorter time intervals when near-fault ground motions have pulse-like characteristics. Results also indicate that for cases in which the natural period of a slope is close to the period of the pulse of a recorded ground motion, an equivalent wavelet pulse appropriately represents the displacement response of slopes. Predictive models are developed for the sliding displacement of near-fault ground motions using spectral acceleration and peak ground velocity as predictive variables. In addition, it is shown that for certai...

Field Measurement and Analysis of Ground Vibration Induced by High-Speed Train

In situ test data for ground vibration of high-speed railways is valuable but scarce. Chinese researchers used to cite test results from European countries to verify their numerical model, owing to the lack of open access to in situ data. To remedy this shortage, this paper presents field measurements of ground vibrations induced by high-speed trains at a site on the Qin-Shen Line in China. The free field vibrations at different distances from the track center during the passage of a high-speed train at a speed varying from 230 to 250 km/h are measured. The recorded vertical accelerations are analyzed both in the time and the frequency domains. The periodic exciting action of the train wheel-set can be identified in the vertical acceleration time-history when the test site is close to (e.g. 3.5 m away from) the track centerline. Vertical acceleration generally attenuates with distance from the track centerline, but a vibration boom occurs at the distance of 12 m. The effect of both P and S waves cannot be neglected in the vicinity of the track, while R waves begin to dominant beyond the distance of 15 m. In addition, an important frequency in the acceleration spectrum of the ground vibration is the fundamental axle passage frequency (25.6–27.8 Hz). The test results could be available to peer researchers for verification of their numerical models, and meanwhile act as a complementary material to currently scarce in situ tests results.

Micro-vibration Measurement and Analysis of High-Tech Electronics Workshop in Guangzhou

High-tech electronics workshop typically has stringent requirements for micro-vibration control, so as to ensure the proper operation of the installed vibration-sensitive facilities. Based on a micro-vibration measurement on a high-tech electronics workshop in Guangzhou, China, this paper reports the test data, presents a systematic and detailed summary of issues related to vibration data processing, and analyzes the transformation of the vibration characteristics when the anti-vibration techniques enhances. The results show that, the one-third octave band spectral has great advantages in representing vibration data of high-tech buildings. With the enhancement of the anti-vibration techniques, the vibration amplitudes in all of the three directions decrease both in time-history and one-third octave band spectral and finally become roughly the same; and the dominant high-frequency component disappears, while the relative low-frequency component takes the leading role in all the three directions.