本研究旨在利用向量式有限元(Vector Form Intrinsic Finite Element)模擬含防止落橋裝置、非線性阻尼裝置隔震橋梁於大地震時之非線性動態反應。依據過去研究顯示，隔震橋梁於大地震中可能產生相當大的位移反應，而採用防止落橋裝置可避免橋面版發生落橋災害，或採用阻尼裝置降低隔震橋梁之位移反應。向量式有限元為一新近發展之結構分析方法，相較於傳統有限元素方法，向量式有限元對於有大變形、大變位或剛體運動之問題，能以更簡易之運算處理。因此本研究選用向量式有限元模擬含防止落橋裝置及非線性阻尼裝置隔震橋梁之動態反應，此瞭解橋梁在強震作用下各構件之互制效應與破壞順序。 為此，本研究開發新非線性元素與新分析功能於向量式有限元素法，新非線性元素包含雙線性彈簧元素(Bilinear Spring)、具可開孔彈簧元素(Gap or Hook Spring)、凱文阻尼元素(Kelvin Damper)、麥斯威爾阻尼元素(Maxwell Damper)及柏格斯阻尼元素(Burgers’ Damper)；新分析功能包含雷利阻尼分析(Rayleigh Damping Analysis)、滑動摩擦分析與構件斷裂模擬等，經由算例與有限元素方法(SAP2000)相較，證實所發展之新元素與新分析方法之正確性，最後以一座隔震橋梁為目標，進行參數探討強震下防止落橋裝置與支承、橋墩間之相互影響關係及極限狀態下之破壞模式，以及不同型式之阻尼裝置減震效果並比較。 Isolated bridges have been extensively used to mitigate the induced seismic forces by a shift of natural period. However, the deck displacement becomes excessively large when subjected to a ground motion with large intensity or unexpected characteristics. Such a large displacement may result in unseating of the deck. Therefore, unseating prevention devices and dampers are important particularly for isolated bridges.This study is aimed to analyze the isolated bridges with unseating prevention devices and nonlinear dampers which may exhibit nonlinear dynamic behavior under large earthquakes. The Vector Form Intrinsic Finite Element (VFIFE), a new computational method developed by Ting et al. (2004), is adopted in this study because the VFIFE has the superior in managing the engineering problems with material nonlinearity, discontinuity, large deformation and arbitrary rigid body motions of deformable bodies. It is selected to be the analysis method in this study. However, the VFIFE is in its infant stage as compared to the conventional Finite Element. There are still a number of elements and analysis method to be developed. Some kinds of new VFIFE elements and analysis methods are herein developed for analyzing the target bridges. Through numerical simulation of examples and comparison with the Finite Element analysis, the developed elements and analysis methods are verified to be feasible and accurate. Finally, we analyze an isolated bridge to investigate the extreme functions of the isolators, columns and unseating prevention devices and to predict the collapse situation of target bridges.
