Track Irregularity Induced by Creeping of Pre-stressed Concrete Bridge, and Its Influence of Riding Comfort

台灣高速鐵路於二〇〇七年通車至今已約五年，土建設施距完工也約快十年，高速鐵路全線約三百四十五公里，其中高架路段約佔全約的百分之七十三，國內長跨高架橋多採用預力混凝土橋樑。混凝土抗拉能力較小，抗壓能力較強，一般混凝土橋樑在自身重量的狀況下會向下彎曲變形，為了抵消並平衡橋樑自重的向下彎曲變形，在混凝土製造階段加入預力使混凝土中性軸以下因預力鋼腱之張力內拉使混凝土承受額外壓力以平衡抵消自重的變形，加入預力鋼腱的混凝土稱為預力混凝土，較一般非預力鋼筋混凝土具抗彎能力，因此廣泛地被運用於橋樑工程。而混凝土具潛變特性，混凝土於長期受力下會發生潛變導致應力逐漸降低。台灣高鐵早期設計預力時考慮較重的列車車輛以及道碴軌道結構，而最終台灣高鐵使用較輕列車及無道碴軌道結構，因此設計預力值偏高，可能造成高架橋樑有過度上拱的情況發生。高速鐵路列車營運時速高達三百公里，混凝土因潛變引起橋面變形而導致軌道線形改變對於行車的舒適度是否有影響為值得研究的課題。 本文採用CEB-FIP 1995的規範計算潛變係數，列車及高架橋模型依據台灣高鐵700T型列車及高架路段建立，為了減少邊界效應的影響，本研究中建立五跨高架橋，使用ANSYS有限元素分析軟體進行潛變分析，將潛變不同時間之變形量加至原模型並產生新的有限元素模型，利用LS-DYNA有限元素分析軟體進行動態分析列車及高架橋特定檢核點之加速度、速度及位移等動態反應。最後將LS-DYNA有限元素分析軟體所得之動態分析結果利用ISO 2631-4評估列車在潛變及軌道不平整之影響下的垂向及橫向振動舒適度。This paper studied the effect of long term concrete creeping behavior of pre-stressed concrete bridge on the vibration of track structure and ridding comfort of high speed rail. Track irregularity can be induced by creeping of pre-stressed concrete bridges. The finite element analysis software ANSYS was used in this paper to calculate the deflection of viaduct by concrete creeping. To consider the pre-stressed effect, we build a five-span concrete bridge model with pre-stressed tendons and calculate the creep coefficient according to the code of CEB-FIP 1995. Vertical deflections by concrete creeping in 20 years were presented in several period. A 4-carbody train passing through deflected bridge in different creeping time was taken into consideration. We use the finite element analysis software, LS-dyna, to perform dynamic analysis. The total accelerations on the car were calculated and the riding comfort was evaluated by ISO 2631-4(2005)