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。因此本研究主要探討含防止落橋裝置之不同支承型式橋梁於大地震時極限狀態的反應。 本研究採用新近發展之向量式有限元素(Vector Form Intrinsic Finite Element)為結構動力分析方法，VFIVE適用於處理大變形、大變位、材料非線性與剛體運動等問題，但過去VFIFE使用中央差分法處理雷利阻尼相關問題時會有數值發散現象，所以本文改採用隱式Newmark-β直接積分求解運動方程式，研提增量迭代計算程序，求得下一步時間之位移、速度與加速度反應，同時計算構件回復內與阻力內力，成功避免高度非線性反應時之發散情形。 本研究以一座六跨簡支梁橋、一座二單元三跨剛性支承連續梁橋和一座二單元三跨隔震支承連續梁橋為目標橋梁，經數值分析結果，三座橋梁無論有無裝設防落裝置，或是防落裝置連接兩相鄰上部結構亦或連接於上部結構與橋墩，均並未提高橋梁發生落橋之地表加速度，且發現剛性支承連續橋之耐震能力高於剛性支承簡支橋和隔震支承連續橋。 In the past extreme earthquake, observed from the damaged bridges, bearing failure, column failure and deck unseating caused a more serious loss. Therefore, it is full of curiosity that how large earthquake will cause a bridge to collapse and how the ultimate state will be. This study is aimed to analyze the ultimate situation of bridges with rigid bearing system and isolated bearing system through numerical analysis. The Vector Form Intrinsic Finite Element (VFIFE), a new computational method 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. In the past, VFIFE was used Central Different Method to be analysis method, there are numerical disperses when to solve the Rayleigh damping analysis. Implicit time integration method(Newmark-β) is adopted in VFIFE . Incremental formulation of the equation of motion is used to do iteration and to solve the response at next time step (i+1) including the displacement, velocity and acceleration. Furthermore, this calculation is also used to calculate the internal resultant force and the internal damping force exerted by the elements surrounding the particle. Three types of bridges, a six-span simply-supported bridge, a continuous-span bridge with hinge and roller bearings and a continuous-span bridge with high-damping-rubber isolators, are analyzed. Through numerical simulation of three bridges with or without unseating prevention devices, the ultimate states are demonstrated and compared. The results show that the unseating prevention devices do not increase the safety of the studied bridges as expected and the performance of the continuous bridge with rigid bearings is better than simply-supported bridge the and isolated bridge to prevent unseating of the superstructure.
