列車行經高架軌道系統造成大地振動評估

Analysis of Ground Vibration Induced by Moving Trains on Viaduct

洪振發(Chen-Far Hung) ； 許維倫(Wei-Lun Hsu)

《應用聲學與振動學刊》 7卷1期 (2015/06) Pp. 33-45

https://doi.org/10.6282/JASV.2015.7.1.04

摘要

軌道系統由於軌道系統列車車輪軸距及行經路線固定等原因，易對鄰近環境持續造成振動之負面影響，尤其以大眾捷運系統，常緊鄰建築，因此在軌道系統在興建前必須對行經路徑周圍進行評估，並針對敏感路段進行精確的振動分析。臺灣目前評估新建之軌道系統造成之振動多依據美國運輸部FTA報告[1]。而該報告之評估方式多根據經驗法則與簡化公式進行，未能準確預估其引致之振動量及頻譜。本文以3D有限元素方法對列車以不同車速通過高架橋梁所引致鄰近大地環境振動進行探討，首先以過去文獻之分析結果比較LS-DYNA計算大地振動之分析結果，並考慮大地模型與橋梁結構模型分析不同車速通過引致大地振動傳播狀況，就車橋共振速度、車速、大地參數、基礎結構形式等影響進行探討，最後提出地表振動量與車速及距離之關係圖。而過去少有車橋共振與大地振動關係之研究文獻，本文特別就此兩者關連進行研究，而由分析結果發現當列車以相對低速之50 kph通過35m連續簡支橋跨時，易激發列車垂向振動且同時放大地表振動反應，與過去所認知之車速越高造成地表振動量越大之印象有所落差。此外由分析結果發現當橋梁基礎型式不同時地表振動傳遞行為、頻譜分布亦有所不同，進而得到地表振動頻譜亦與鋼軌扣件間距有所關連，因此透過調整扣件間距之方式應可避開鄰近建物之振動敏感頻率，進而減少軌道系統對於環境之影響。

關鍵字

有限元素法 ； 大地振動 ； 軌道橋梁 ； 車橋共振

並列摘要

Railway system has constant axle distance, and heavier axle load than the highway system. While the train passing by, the ground vibration propagated from viaduct is easily to induce low-frequency vibration and impact the neighbor buildings continuously. Prediction of ground vibration induced by moving trains can follow guide of FTA report. But the prediction method proposed by FTA is based on statistics data and empirical method can't accurately analyze vibration spectrum and ground vibration propagation when the train is passing by. In this paper the 3D FEM is used to calculate the ground vibration induced by trains and bridges interaction and which was rarely been discussed in the past literature. Effects of different bridge foundation types, ground characteristics, train speed and train-bridge resonant conditions on the ground vibration were examined. Finally, the distribution of ground vibration level versus train speed, distance form pier has been summarized, and found when train passing 35 m simple support bridges by speed 50 kph will matches vertical resonance frequency of suspensions and enlarge ground vibration level. Furthermore, form the analyzed results different bridge foundation and different rail fastener pitch will also leads to different ground vibration spectrum and behavior. In the future, modify the fastener pitch would be one of solutions to avoid the sensitive frequency and reduce the impact the neighbor buildings on the railway path.

並列關鍵字

FEM ； Ground Vibration ； Viaduct ； Train- Bridge Interaction