跨越斷層橋梁之極限動力分析

近二十餘年世界所發生災害性地震中，已獲得相當多近斷層強地動紀錄，近斷層地表運動相較於遠域地表運動，其特色在於震波中含有長週期速度脈衝。1999年台灣921大地震中引發地震之車籠埔斷層沿線，十餘座橋梁發生嚴重損壞，除強烈地表運動外，斷層沿線最大達8公尺之錯動位移乃橋梁損壞甚至崩塌之主要原因。長久以來，跨越斷層橋梁應採何種橋型一直為橋梁工程師難解的課題，究其原因乃缺乏適當分析技術，驗證橋梁一旦遭受地表錯動位移時之動力行為，因此無從判斷各種橋型之優缺點。本研究採用新近發展適用於處理大變形、大變位、材料非線性與剛體運動等問題之向量式有限元素法為結構動力分析方法，以六跨簡支梁橋、兩座三跨連續梁橋、兩座三跨剛接橋與六跨連續剛接橋為目標橋梁，輸入含地表錯動位移之近斷層地震波，預測橋梁極限破壞狀態。經由參數分析結果，比較各橋型之橋面板落橋、橋墩柱底塑鉸破壞與橋墩剪力破壞數目，瞭解各橋型於斷層錯動時之破壞坍塌情況，更重要為闡明各橋型之破壞機制，並比較其優缺點，本研究成果可提供橋梁實務規劃設計之參考。

關鍵字

極限破壞；近斷層地震；橋梁；向量式有限元素法；非線性動力分析

並列摘要

In the past two decades, a number of near-fault ground motions have been recorded in major earthquakes, such as the 1995 Japan Kobe earthquake and the 1999 Chi-Chi earthquake. Near-fault ground motions comprise long-period pulses, which is unique as compared to far-fault ground motions. Numbers of bridges along the Chelungpu fault suffered damage, even collapsed, during the Chi-Chi earthquake. Those can be attributed to not only the strong ground motions but also ground dislocation. How to design a bridge crossing a fault is still an open issue nowadays because there is no a feasible computation technology. Therefore, it is impossible to determine the type of bridges when they span an active fault. The Vector Form Intrinsic Finite Element (VFIFE) is superior in managing the engineering problems with material nonlinearity, discontinuity, large deformation, large displacement and arbitrary rigid body motions of deformable bodies. The VFIFE is thus selected to be the analysis method in this study. Four types of bridges, including a six-span simply-supported bridge, a three-span-continuous bridge, a three-span-rigid bridge and a six-span-rigid bridge, are analyzed to predict the failure situation under near-fault ground motions with dislocation. Through a serious of parametric studies, the failure modes are demonstrated for the four types of bridges. Importantly, the failure mechanism of all the bridges is clarified so as to compare the feasibility of four types of bridges when designing bridges crossing a fault. The simulation results should be applied to practical implementation.

並列關鍵字

ultimate state ； nonlinear dynamic analysis ； bridge ； VFIFE ； near-fault ground motion

參考文獻

[1]Ting, E. C., Shih, C. and Wang, Y. K. (2004), “Fundamentals of a Vector Form Intrinsic Finite Element: Part I. Basic Procedure and a Plane Frame Element.” Journal of Mechanics, Vol. 20, No. 2, pp. 113-122.

[2]Ting, E. C., Shih, C. and Wang, Y. K. (2004), “Fundamentals of a Vector Form Intrinsic Finite Element: Part II. Plane Solid Elements.” Journal of Mechanics, Vol. 20, No. 2, pp. 123-132.

[3]Shih, C., Wang, Y. K. and Ting, E. C. (2004), “Fundamentals of a Vector Form Intrinsic Finite Element: Part III. Convected Material Frames and Examples.” Journal of Mechanics, Vol. 20, No. 2, pp. 133-143.

[4]Wang, C. Y., Wang, R. Z., Kang, L. C. and Ting, E. C. (2004), “Elastic-Plastic Large Deformation Analysis of 2D Frame Structure.” Proceedings of the 21st International Congress of Theoretical and Applied Mechanics (IUTAM), SM1S-10270, Warsaw, Poland, August 15-21.

[5]Wu, T. Y., Wang, R. Z. and Wang, C. Y. (2006), “Large Deflection Analysis of Flexible Planar Frames.” Journal of the Chinese Institute of Engineers, Vol. 29, No. 4, pp. 593-606.

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跨越斷層橋梁之極限動力分析

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