無線感測技術應用於橋梁淘刷檢測之開發與實測

為因應氣候變遷對橋墩淘刷所增加的風險，應對重要橋梁實施安全性監測，本研究利用自製之無線監測網路（Wireless Sensor Network，WSN）系統，對所選橋梁進行微振試驗，以其監測值做快速傅立葉轉換（FFT）後可得到橋墩之自然頻率值，並搭配有限元素模型，以推估橋墩目前的沖刷深度。近年來，開放原始碼（Open Source）風氣盛行，在軟硬體整合與軟體開發上已不如過去封閉，因此本研究採用 Arduino UNO 版進行測試，並自行整合無線傳輸模組、數位類比轉換器等，再以 MATLAB 作為示波器與資料處理用，取代過去受制於套裝之示波器、轉換器或專利保護等限制，期待能因此有更廣泛之使用。以一壽橋為例，利用 WSN 收集訊號，並測試不同資料筆數、各位置傳輸穩定性，並利用快速傅立葉轉換與 Welch Method 將其轉換為頻譜訊號，即可自動出圖並儲存於電腦中，得即時之橋墩頻率，最後得出使用 Welch Method 有較佳之圖形辨識度。而在傳輸過程中，發現其傳輸量並不如產品規格所示，再改用不同傳輸模式後，在封包接收的穩定性已有大幅度的提升，所得一壽橋之主要自然頻率值為 1.897。有限元素模型之建置參數，將以現地實測之橋梁自然頻率作為校正參數，並使用現地鑽探資料設定土壤等值彈簧，不同的最高彈簧深度即代表橋梁淘刷深度，所得之橋梁淘刷與自然頻率關係曲線，即可作為後續判識橋梁淘刷狀況之指標。

關鍵字

橋梁沖刷；結構健康診斷；無線感測網路；微振實驗；橋梁監測

並列摘要

Recently, the climate change has brought great impact on flooding. In order to cope with the increasing risk of scouring caused by flooding, the present study has developed a self-made wireless monitoring network （WSN） system to monitor the bridge dynamic characteristics. This study proposed a new procedure of identifying the structural dynamic characteristics from ambient vibration test of the structure via Fast Fourier Transform（FFT） and Welch method analysis. The natural frequency accessed from the proposed procedure will be compared with the finite element model to estimate the current scouring depth. To build the finite element model, the natural frequency of bridge is used as calibration parameter and the N-value from Geo-technical investigation is used to set equivalent soil spring. To avoid the limitation of patent and software package, the open sources, are used in this study, such as Arduino UNO, wireless transmission module and digital to analog converter are used in this study. Meanwhile, MATLAB is served as an oscilloscope and the data processing tool. This WSN system is expected to be widely used in scouring monitoring of bridge. For the field-implementation, the WSN system is installed on Yishou Bridge for testing the transmission stability and comparing 2 types of Spectrum analysis methods. The study result reveals that the main natural frequency of Yishou Bridge is 1.897 Hz. There are three main result in this research. First, The API transmission mode has shown its effect on enhancing the success rate of transmission. Second, Welch method improves the shortcoming of the FFT by splitting the signal and overlapping segments to reduce the noise. Third, the relationship curve of scouring and natural frequency would be used as an indicator to estimate the bridge scouring situation.

並列關鍵字

Bridge Scouring ； Structure Health Monitoring ； Wireless Sensor Network ； Bridge Monitoring ； Ambient Vibration

參考文獻

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無線感測技術應用於橋梁淘刷檢測之開發與實測

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