以無線感測儀器監測橋梁淘刷之研究-寶橋及萬壽橋為例

Abstract

全球氣候變遷，極端氣候增加，大雨使暴漲的溪水不斷淘刷橋梁，如何監測橋梁的淘刷情況，成為一門重要的課題。因此本研究利用無線感測儀器，對橋梁進行微振量測試驗，將測得之加速度值進行快速傅立葉轉換 (FFT )及Welch Method分析，取得橋梁之自然頻率，實測的自然頻率再與有限元素模型結果比對，推估出橋墩目前的淘刷深度，藉此確立監測橋梁淘刷深度之方法。 目前市面上已有多種微振量測儀器，但以有線量測儀器居多，且儀器價格高昂，對於現地監測較不適用，故本研究利用無線感測儀器進行實測，無線感測儀器採用加速度計MMF KB12VD，以及使用Arduino Uno、Xbee無線傳輸模組等開源軟體(Open Source)，進行資料蒐集與傳輸，再以MATLAB 作為資料處理及示波器，取代一般商用儀器專利保護限制，對後續橋梁監測上能有更廣泛的應用。 模型建置採用SAP2000有限元素軟體，首先取得寶橋及萬壽橋的竣工圖及後續補強圖，依橋梁現況進行模型建置，且確立邊界設定，土壤的部分以土壤等值彈簧進行模擬，藉此分析出結構自然頻率與淘刷深度關係圖。 本研究將無線感測儀器放置在各橋柱的樁帽上以及橋面板的上游側、下游側，由試驗與模擬結果對照，顯示將無線感測儀器放置於橋面板下游側水流方向，所量測到的數值最接近橋梁自然頻率，此位置淘刷深度絕對誤差-102.08~+53.5公分，頻率相對誤差-0.63%~+1.3%。研究結果顯示，監測橋梁淘刷深度之方法對於寶橋及萬壽橋皆適用，因此以無線感測儀器監測橋梁淘刷程度應具有可行性。

Due to global climate change, extreme climates have increased. Heavy rain caused the stream to rise, increasing the risk of scouring the bridge. How to monitor the scouring of bridges has become an important issue. Therefore, this study uses wireless sensing instruments to identify the structural dynamic characteristics from Ambient Vibration Test of the structure. Then convert the acceleration to the natural frequency of the bridge by Fast Fourier Transform and Welch method analysis. The measured natural frequency is compared with the results of the finite element model to estimate the current scouring depth of the pier. This study uses wireless sensing instruments. It is composed of accelerometer (MMF KB12VD) and open source software (Open Source) such as Arduino Uno and Xbee wireless transmission module, etc. The instrument collects and transmits data, and then uses MATLAB as the data processing and oscilloscope. In this way, the limitation of patent protection can be avoided, and it can be more widely used in subsequent bridge monitoring The model is built by finite element software SAP2000, in this study. Firstly, the completion drawings and subsequent reinforcement drawings of Bao Bridge and Wanshou Bridge are obtained. Build the model according to the actual condition of the bridge and establish the boundary settings. The soil part is simulated with an equivalent soil spring. Based on this, the relationship between the natural frequency of the structure and the depth of scrubbing is analyzed. In this study, wireless sensing instruments were installed on the pile caps of each bridge column and the upstream and downstream sides of the bridge deck. Compare the Ambient Vibration test with the simulation results, the value, which is analyzed by installing the wireless sensing instrument on the downstream side of the bridge deck, is closest to the natural frequency of the bridge. The relative error of frequency is -0.63% ~ +1.3%, and the absolute error of scouring depth is -102.08 ~+53.5 cm. The research results show that the method of monitoring bridge scouring depth is applicable to both Bao Bridge and Wanshou Bridge. Therefore, it should be feasible to monitor the scouring depth of bridges with wireless sensing instruments.