依據過去地震經驗發現橋梁常遭受嚴重之損害，而橋梁支承裝置、橋柱之損壞與落橋所造成的損失更為嚴重，為模擬橋梁於強震中極限破壞情形，本研究旨在開發新纖維元素模型(Fiber Element)建立橋梁塑鉸處構件，模擬橋梁於強震中塑鉸產生之高度非線性行為。本研究採用向量式有限元素(Vector Form Intrinsic Finite Element)為結構動力分析方法，此方法適用於處理大變形、大變位、材料非線性與剛體運動等問題。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，但是此行為並無法精準模擬真實斷面降伏時，斷面由外至內依序降伏之實際情況。為模擬斷面實際降伏情況， 本研究引入纖維元素方法(FiberElement Method) 取代雙線性彈簧元素(Bilinear Spring) ，以纖維元素的應力應變數值計算準確模擬塑鉸欲達極限破壞之高度非線性行為，並配合Newmark-β法增量迭代計算程序，更新纖維元素方法中桿件狀態判定參數與斷面參數程序計算桿件內力，再經由算例分析，證實所發展之新元素與新分析方法之正確性。最後以一座三跨剛性支承簡支橋梁為目標，進行參數分析探討在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In the past extreme earthquake, observed from the damaged bridges,bearing failure, column failure and deck unseating caused a more seriousloss. Therefore, it is full of curiosity that how large earthquake will cause abridge to collapse and how the ultimate state will be. This study is aimed todevelop the new model of Fiber Element in plastic hinge zone, and tosimulate high-degree nonlinear behavior of bridges by strong motion.The Vector Form Intrinsic Finite Element (VFIFE), a newcomputational method is adopted in this study because the VFIFE has thesuperior in managing the engineering problems with material nonlinearity,discontinuity, large deformation and arbitrary rigid body motions ofdeformable bodies. In the past, VFIFE was used Bilinear Spring to analyzeall nonlinear behaviour. It means whole section is yielding and does theplastic behaviour with the enough force. But this is not fit accurately withthe real condition of yielding section.In order to analyze the real condition of the section, using stress-strainrelation to calculate and analyze the high-degree nonlinear behaviour withultimate-destroying of plastic hinge. Because of the formulation ofNewmark-β, it’s very important to renew the iteration type of FiberElement Method to calculate the element internal force. Through numericalsimulation of examples, the developed elements and analysis methods areverified to be feasible and accurate.Finally, we use many contact models in three elastic rods and analyzean simple bridge to investigate the extreme functions of the columns andunseating prevention devices between Fiber Element and Bilinear Spring,and predicting the collapse situation of target bridge.
