隨著高速鐵路建設的蓬勃發展，列車車速的提升對軌道結構與地面所產生的動態影響也趨強烈，對於軌道剛度不夠或軟弱路基土壤路段，高速列車誘發強烈振動將使軌道結構嚴重破壞，甚至導致列車出軌，影響列車行駛安全。
　　為探討列車行駛速度與軌道結構動態響應，本研究透過ABAQUS有限元素法軟體建立列車荷重-軌道結構模型，模擬軌道結構受移動荷重作用，並以荷重速度於臨界速度下為研究主軸，分析軌道結構振動動態反應。
研究結果顯示，隨著列車車速的提升，軌道結構振動逐漸增大。當列車行駛速度達到軌道臨界速度的0.6倍以上時，速度所產生的動態影響與多輪荷重疊加效應漸趨明顯；當移動速度趨近軌道臨界速度時，軌道振動急劇增加，嚴重影響列車行駛安全。而隨著荷重速度與基礎阻尼參數的不同，在荷重點前後方亦分別產生不同頻率波幅的振動，軌道產生最大變位的速度也隨著的阻尼提高而下降。此外若荷載速度低於軌道臨界速度時，提高軌道基礎彈性勁度、提高軌道剛度或減少軌道參振質量對於減小軌道振動動態反應並不明顯；但隨著荷載速度趨近軌道臨界速度時，提高軌道基礎彈性勁度、提高軌道剛度或減少軌道參振質量對減小軌道振動動態反應則越趨明顯。

　　With the trend of increasing speed and capacity, the railway structures are facing more and more challenges. When the train speed approach the critical wave velocities of the track structure, the deformations of track systems may increase dramatically due to resonance and result in track failure and even derailments. This study applied the finite element analysis package, ABAQUS, to model track structures loaded by high speed moving suspended mass to investigate the interactions among track structure parts and track responses.
　　The results of this study showed that raising train speed may significantly increase track vibrations. When the train speed approached the critical velocity of the track system, the analysis considering multiple axle loads illustrated different train-track behavior from the results with single moving axle. It was also concluded that stiffening track rigidity by improving subgrade quality is a cost-efficient way to cope with the challenges on track structures in the high-speed railway transportation era.

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