考量斷層錯動與塑鉸破壞之橋梁極限分析

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题名:	考量斷層錯動與塑鉸破壞之橋梁極限分析
作者:	陳怡文;Chen,Yi-Wen
贡献者:	土木工程學系
关键词:	向量式有限元素法;近斷層地震;纖維元素法;極限狀態;橋梁
日期:	2013-10-03
上传时间:	2013-11-27 11:21:21 (UTC+8)
出版者:	國立中央大學
摘要:	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公尺錯動位移乃橋梁損壞甚至崩塌之主要原因。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(Vector Form Intrinsic Finite Element)為結構動力分析方法，以兩座三跨連續梁橋為目標橋梁，進行三維動力分析，輸入含地表錯動位移之近斷層地震波，經由參數分析結果，比較橋梁於水平橫向、縱向與垂直向組合地表錯動作用下之橋面板落橋、橋墩塑鉸與剪力破壞數目，瞭解連續梁橋於斷層錯動時破壞模式，並進行支承參數分析，深入探討支承破壞強度對於整體橋梁耐震能力與崩塌型式之影響。此外，過去VFIFE使用雙線性彈簧元素(Bilinear Spring)模擬所有非線性行為，即構件受力達一定強度，全斷面降伏並同時進入塑性行為，但此行為無法精準模擬真實斷面由外至內依序降伏之實際情況。故本研究引入纖維元素法(Fiber Element Method)，以纖維元素之應力應變數值計算準確模擬塑鉸達極限破壞之高度非線性行為，配合Newmark-β法增量迭代計算程序，並經由算例分析，證實所發展之新元素與新分析方法之正確性。最後以一座五跨隔震支承連續橋梁為目標橋梁，進行參數分析探討於三種不同測站之強震下，橋墩柱底塑鉸分別使用纖維元素與雙線性彈簧元素時，橋梁防止落橋裝置與支承、橋墩間之相互影響關係，探討橋梁於地震發生時在極限狀態下之破壞模式。 In the past two decades, a number of near-fault ground motions have been recorded in major earthquakes, such as 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. 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 3-D analysis method in this study. A three-span-continuous bridge is analyzed to predict the failure situation under 3-D near-fault ground motions with dislocation. Through a serious of parametric studies, the failure modes are demonstrated for bridges. Besides, the failure mechanism of bearing system is clarified so as to compare the feasibility of different bearing system. And in order to analyze the real condition of the section, this study is aimed to develop the new model of Fiber Element that using stress-strain relation in plastic hinge zone to simulate high-degree nonlinear behavior of bridges by strong motion. Implicit time integration method (Newmark-β) is adopted to renew the iteration type of Fiber Element Method to calculate the element internal force. Finally, this study analyzes a five-span-continuous isolated bridge to investigate the extreme functions of the columns and unseating prevention devices between Fiber Element and Bilinear Spring, and predict the collapse situation of the target bridge.
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