橋梁頻率間接量測法之實驗研究

Abstract

橋梁的整體性檢測在以往不外乎針對橋梁結構進行動力反應之量測，藉以得知橋梁所蘊含的力學特性。傳統量測主要利用直接安裝在橋梁主體上的感應器，對橋梁作直接的振動量測，吾人稱之為直接量測法。而近年來橋梁整體性檢測技術日新月異，由車橋互制理論所衍伸出來的間接量測概念，已成為近年來不少學者所致力研究的課題。相較於直接量測法，間接量測法只需藉由裝置在移動車輛上的感應器，就可擷取到待測橋梁之振動頻率，具有移動性、迅速性、經濟性等優勢。然而過去對於間接量測法的研究重心，主要以橋梁或移動車輛之數值模擬、參數分析以及初步之現地試驗為主，目的在於證實間接量測法在理論上及實際上之可行性，但在實際量測中，影響擷取橋梁頻率成功機率甚鉅的試驗車體，在過去並不曾進行過整體性之研究。本研究的目的乃利用系統的實驗方式，藉由實際的車體試驗及現地試驗過程中，不斷改善試驗車體及相關設備，以得到更好的間接量測橋梁頻率之效果。本論文的研究成果，證實了試驗車體本身的動力性質對間接量測法在施行上之重要性，也證實藉由針對試驗車體本身以及輪胎性質做的改進，可在實際的的橋梁實驗中得到更好的實驗效果。最後則提出幾點結論，以供後續的現地試驗及研究方向做為參考。

Engineers are interested in the dynamic characteristics of bridges via field measurements. To obtain the dynamic response of a bridge, traditional measurement approaches require several sensors to be installed on the bridge deck. Such approaches are referred to as the direct approaches. Recently, some progress has been made on the global measurement techniques of bridges. Yang and his co-workers (2004) presented a new concept for measuring the bridge frequencies from the dynamic responses of a passing vehicle. Such an approach is referred to as the indirect approach, which is advantageous over the direct approaches in terms of portability, convenience, and economics, due to the fact that it requires sensor(s) being installed on the vehicle instead of on the bridge. However, previous researches along these lines were focused on numerical simulations, parametric studies, and preliminary field tests, for the purpose of verifying the feasibility of the indirect approach theoretically and experimentally. As for the test vehicle, which greatly affects the probability of successfully identifying the bridge frequencies, was not studied thoroughly. Therefore, the objective of this study is to enhance the indirect approach for measuring the bridge frequencies by improving the test vehicle and related instrumentation through the repetition of the vehicle tests and field tests. In this study, the test results indicate that the dynamic characteristics of the test vehicle is crucial to the indirect approach and that better identification results can be obtained in practical bridge measurements by improving the test vehicle structure and tires materials. Finally, concluding remarks are drawn for further field tests and future researches at the end of this study.