| 摘要: | 南方澳大橋於民國108年10月1日上午發生橋身突然倒塌的事件，突顯橋梁安全維護的重要性，關渡大橋目前橋齡已超過40年，橋梁服務性及安全在下列情況可能存在疑慮，因此本研究針對橋體結構及纜索作數值模擬。
文獻回顧內容包含索力計算方法、關渡大橋纜索之結構及其材料性質，以進行後續建模及數值驗證。
索力分析中第一部分為彎曲剛度分析，模擬纜索在不同角度下受彎矩作用後的彎曲剛度，最後整理出平均值，並將結果用於後續模擬；第二部分為研究纜索各構件對頻率的影響，將纜索模型分為4個類型，比較不同模型下的頻率差異，以決定後續全橋模型中纜索的簡化方式。
全橋分析根據關渡大橋竣工圖建立數值模型，流程包括以Solid Works建出外觀，Hyper Mesh切出網格元素，Ls-Dyna輸入材料、結構構件的定義及邊界條件設定。分析包含模態分析、靜載分析、溫度分析、地震力分析。模態分析初步確認模型是否有誤，以及得到關渡橋之自然模態頻率。靜載分析中先模擬無施加索力的分析，取得纜索因橋拱及主梁受重力變形後所造成的索力，與監測數據做比較，藉以判斷監測數據的正確性；後為模擬施加索力的分析，以監測索力為目標索力對模型進行調整，模擬現今監測索力及重力對橋體變形的影響。溫度分析概念為排除車載，溫度對監測索力的影響，因此取凌晨時段之監測數據，再由該部分的數據中取相對高溫及低溫的數據，比較溫度對實際監測的影響，後於模型中數據對應之溫度，比較有限元模型模擬出之數據是否對應監測數據。
;The Nanfang′ao Bridge suddenly collapsed on the morning of October 1, 2018, highlighting the importance of bridge safety maintenance. The Guandu Bridge is currently over 40 years old, and the serviceability and safety of the bridge may be questionable under the following circumstances. The research conducts numerical simulations on the bridge structure and cables.
The literature review includes the cable force calculation method, the structure of the cable and its material properties for subsequent modeling and numerical verification.
The first part of the cable force analysis is the bending stiffness analysis, which simulates the bending stiffness of the cable after being subjected to bending moments at different angles. Finally, the average value is compiled and the results are used for subsequent simulations; the second part is the study of the frequency response of each component of the cable. The cable model is divided into 4 types, and the frequency differences under different models are compared to determine the simplification method of the cable in the subsequent full-bridge model.
The full bridge analysis establishes a numerical model based on the as-built drawings of the Guandu Bridge. The process includes using Solid Works to create the appearance, Hyper Mesh to cut out the mesh elements, and Ls-Dyna to input the definition of materials, structural components, and boundary condition settings. The analysis includes modal analysis, static load analysis, temperature analysis, and seismic force analysis. Modal analysis preliminarily confirms whether the model is correct and obtains the natural modal frequency of Guandu Bridge. In the static load analysis, the analysis without applied cable force is first simulated, and the cable force caused by the gravity deformation of the bridge arch and main beam is obtained, and compared with the monitoring data to judge the correctness of the monitoring data; then the cable force is simulated for the simulation. Force analysis, the model is adjusted with the monitoring cable force as the target cable force, and the influence of the current monitoring cable force and gravity on the bridge deformation is simulated. The concept of temperature analysis is to exclude the influence of vehicle temperature on the monitoring cable force. Therefore, the monitoring data in the early morning period are taken, and then the relatively high and low temperature data are taken from this part of the data to compare the impact of temperature on the actual monitoring, and then in the model The temperature corresponding to the data is compared to see whether the data simulated by the finite element model corresponds to the monitoring data. |
