橋梁頻率間接量測法之研究

Indirect Approach for Measuring the Bridge Frequencies from a Passing Vehicle

張凱淳(Kai-Chuen Chang)

指導教授 ： 楊永斌

國立臺灣大學/工學院/土木工程學研究所/博士(2009年)

https://doi.org/10.6342/NTU.2009.02744

摘要

傳統上，量測橋梁頻率的方法是，直接安裝感測器於橋體上，經由記錄與分析橋體的振動反應得到橋梁頻率，該方法被稱為橋梁頻率直接量測法。最近，一種被稱為橋梁頻率間接量測法的新概念被提出，此一量測法之主軸為，間接地由車輛於通過橋梁期間之動力反應中擷取橋梁頻率，而不是由橋體的動力反應中擷取之。與傳統的直接量測法相較，利用移動車輛來量測橋梁頻率的間接量測法，擁有移動性、方便性、經濟性等優勢。但在早期對間接量測法的研究當中，焦點著重於該新量測法之可行性研究，因此僅有橋梁的第一頻或基頻被詳加考慮且成功擷取。本研究之目的在提昇橋梁頻率間接量測法之品質，在考量下列幾個方面之後，間接量測法之適用範疇延伸至，能更可靠地量測到基頻及基頻之外的橋梁頻率：(1)確保車輛反應Fourier頻譜中的解析度；(2)評估車橋互制系統中，各主要參數對車輛動力反應之影響；(3)藉由與經驗模態分離法(empirical mode decomposition, EMD)之結合，強化間接量測法；(4)探討採用Hilbert-Huang轉換(HHT)取代或輔助傳統快速Fourier轉換(FFT)之可行性。最後，提出幾點結論，以供後續現地量測及未來研究工作之參考。

關鍵字

橋 ； 橋梁 ； 頻率 ； 橋梁頻率 ； 量測 ； 現地實驗 ； 間接法 ； 參數分析 ； 經驗模態分離 ； 希爾伯特-黃轉換

並列摘要

Conventionally, the bridge frequencies are measured directly from the dynamic response of the bridge, using vibration sensors directly mounted on the bridge. Such an approach is referred to as the direct approach. Recently, another concept for measuring the bridge frequencies, referred to as the indirect approach was proposed. The main idea of the indirect approach is to extract the bridge frequencies indirectly from the dynamic response recorded for a vehicle during its passage over the bridge, rather than from that recorded for the bridge. Compared with the direct approach, the indirect approach for measuring the bridge frequencies from a passing vehicle has the advantage that it is a movable technique; it can be conveniently applied to measuring the frequencies of a bridge with basically no instrumentation on the bridge. In the early stage of studies on indirect approach, focus has been placed on its feasibility. As such, only the first or fundamental frequency of the bridge has been considered in the investigation. The objective of this dissertation is to refine the indirect approach for extracting the bridge frequencies. The applicability of the indirect approach is extended to extracting bridge frequencies other than the fundamental one with higher reliability, taking into account the following factors: (a) to ensure resolution in the Fourier spectrum of the vehicle response, (b) to evaluate how each of the major parameters of the vehicle-bridge system may affect the dynamic response of a passing vehicle, (c) to enhance the indirect approach by combining it with the empirical mode decomposition (EMD) technique, and (d) to explore the feasibility of applying the Hilbert-Huang transform (HHT) as an alternative or joint tool for the conventional fast Fourier transform (FFT). Suggestions are made for later application of the technique in the field, along with further directions of research highlighted.

並列關鍵字

bridge ； frequency ； bridge frequency ； measurement ； field test ； indirect approach ； parametric study ； Fourier spectrum ； empirical mode decomposition ； EMD ； Hilbert-Huang transform ； HHT

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