TAISEI�@YABUTA

Fundamental study on the state of expansion device using in-vehicle vibration accelerometer

YASUYUKI�@MIYAKI

The purpose of this study is to quantitatively and simply grasp the state of the expansion device, to determine the relationship between the in-vehicle vibration acceleration generated when the vehicle passes through the expansion device and the state of it. So, to verify the relevance and propose one of the inspection work techniques, the in-vehicle vibration acceleration, emphasizing simplicity, was measured using a smartphone DRIMS system with a sampling frequency of 100 Hz. Because it is difficult to accurately grasp the state of the expansion device without traffic regulation, in addition, measuring the in-car vibration acceleration of an actual bridge, an experiment using an acrylic plate simulating the expansion device of the Chosei Bridge was performed.
The obtained measurement results were evaluated using three items of effective value, maximum total amplitude, and waveform and frequency analysis, and the relevance was verified. From the experimental results, no clear difference in the effective value, maximum total amplitude, and waveform due to the difference in the type of expansion device were found. However, a clear difference was confirmed in the waveform and frequency spectrum of each expansion device, indicating that the vibration acceleration in the vehicle was significantly affected by the state of the expansion device. Also, from the results of the model experiment and the steps of the Chosei Bridge, there was little correlation between the vibration acceleration and the gap, but there was a strong correlation between the effective value of the vibration acceleration and the steps. The effect of the step was found to be strong.
 From the results, it is difficult to determine the type of the expansion device from the in-car vibration acceleration, but it is possible to grasp the steps and changes in the state by measuring the in-car vibration acceleration periodically. In the future, it will be necessary to create a standard for determining the state of the expansion device from changes in the effective value, waveform, and frequency spectrum of the vehicle's vibration acceleration and it will be necessary to measure the acceleration over time.