Application of the vehicle-bridge interaction theory to indirect approach for measuring bridge frequencies
Date Issued
2014
Date
2014
Author(s)
Wu, Yu-Hsuan
Abstract
It is an important issue to confirm the safety of bridges after the occurrence of a natural disaster, such as typhoons and earthquakes. The conventional method for identifying bridge dynamic properties is to analyze the dynamic response of the bridge via the vibration sensors directly mounted on the bridge. Through the use of proper analysis techniques, the frequencies, mode shapes or damping ratios of the bridge can be obtained. Such an approach has been referred to as the direct approach.
In recent years, in order to improve the shortcomings of the direct approach, another concept called the indirect approach had been proposed. The key concept of the indirect approach is as follows: We let a test vehicle installed with sensors to pass the bridge of concern. While the bridge will be excited by the test vehicle, the response of the vehicle is also dominated by the bridge. Therefore, the response recorded of the vehicle during its passage over the bridge will contain the information of the bridge. Such a fact allows us to extract the modal parameters of the bridge from the dynamic response of the vehicle in an indirect way. Because of its mobility, the indirect method can be effectively used to identify the dynamic properties of a number of bridges in a region after the occurrence of a major natural hazard. Such information is crucial to detection of damages and evaluation of structural soundness of the bridges.
The objective of this study is to investigate the indirect approach of bridge frequency measurement by numerical simulations. We shall start from the basic vehicle-bridge interaction theory. Second, we shall introduce the signal processing methods such as the fast Fourier transformation, frequency domain decomposition, and the matrix identification method based on the power spectral density, tailored specifically for the the indirect approach. We will investigate the response of the test vehicle traveling over bridges with smooth road surface. The we will proceed to consider the influence of road roughness on the vehicle response. Also, we shall extend the model to include the effect of varying speeds for the vehicle to examine the result under more general scenarios using various examples. At last, we shall investigate the feasibility of damage identification under the special scenario of using three identical vehicles moving with the same speed and spacing over the bridge. The conclusions accumulated in all previous chapters for the effects studied will be summarized in the concluding chapters, along with the directions for future research outlined.
Subjects
橋梁頻率
損傷識別
路面粗糙度
訊號處理
變速度運動
車橋互制
實驗車
Type
thesis
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