車橋互制理論於橋梁頻率間接量測法之應用

Application of the vehicle-bridge interaction theory to indirect approach for measuring bridge frequencies

吳侑軒(Yu-Hsuan Wu)

指導教授 ： 楊永斌

國立臺灣大學/工學院/土木工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.10192

摘要

颱風與地震等天災過後，橋梁的安全性是相當重要的課題。傳統識別橋梁動態特性的方法，是直接將感測器安裝於橋梁上，並利用感測器所量測到的橋梁動力反應，進行分析與識別，由此獲得橋梁頻率、模態或是阻尼比等資訊，此方法稱之為直接量測法；近年來，為了改善直接量測法的缺點，間接量測法被提出，其概念是讓一輛加裝感測器的實驗車輛通過橋梁，車體激盪橋梁的同時，橋體反應也會影響車體，因此，感測器所記錄的車體反應，也隱含了橋體的訊息，此點使得我們可以間接地由車輛反應，獲得橋梁的模態參數，而由於其高機動性的特性，可在天災之後更快速地獲取橋梁模態參數，提供工程師破壞檢測與安全評估之參考依據。
本研究目的在於利用數值模擬進行間接量測法之探討。先從基本的車橋互制理論開始推導，之後引入快速傅立葉轉換(fast Fourier transformation)、頻率域分析(frequency domain decomposition)及因應間接量測法，所提出的功能譜密度函數矩陣識別法(matrix identification method based on the power spectral density)等訊號處理手段，探討一般路面下的間接量測結果，以及考慮路面粗糙度影響下之情況；同時也將車橋互制模型拓展至變速度車輛量測，藉由許多例題分析，探討更廣義的量測情境下間接量測之效果；並且初步探討利用三輛相同、等速、等間距的車輛，進行橋體的損傷識別；最後，根據本文各章的例題分析，吾人將針對各種案例及其效應提出具體結論，以作為未來研究之參考。

關鍵字

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

並列摘要

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.

並列關鍵字

bridge frequency ； damage identification ； road surface roughness ； signal processing ； varying-speed motion ； vehicle-bridge interaction ； test vehicle

參考文獻

李育謙(2011),「濾波技巧於橋梁頻率間接量測法之應用」，國立台灣大學土木工程學系碩士論文

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