目前橋梁耐震設計分析時，通常由假設各橋墩支承之輸入地表運動相同以簡化分析與設計，然而現代橋梁工程已朝向長大橋梁技術發展，對於大跨徑橋梁或多跨徑橋梁，各橋墩支承之地表運動實際上有延滯時差之情形。向量式有限元素為一新近發展之結構分析方法，相較於傳統有限元素方法，其對於有大變形、大變位或剛體運動之問題，能以更簡易之運算方式分析。本研究以極限破壞分析方式，採用向量式有限元素模擬不同支承型式多跨徑橋梁於大地震時極限破壞狀態，同時考量上部結構間之碰撞，探討多跨徑橋梁於多支承輸入地表運動下其動力反應與破壞模式之差異。 本研究以一座十五跨簡支橋梁及三座五跨隔震連續橋梁為分析對象，以四個重要的近斷層強烈震波進行地震波速參數分析，數值分析結果顯示，剛性支承簡支橋考慮多支承輸入時，不僅影響落橋跨數，亦影響其支承破壞順序，且多支承輸入之橋面板落橋數明顯高於同步輸入之落橋數。隔震支承連續橋考量多支承輸入時，除落橋跨數外，亦改變其發生落橋之原因，但多支承輸入之橋梁崩塌情況較同步輸入崩塌情況嚴重。本研究成果顯示多跨度橋梁於強烈地震下，動力分析若採用同步地表運動輸入方法，無法模擬橋梁真實之動力行為，因此建議多跨度橋梁設計分析時，應採用多支承輸入，避免設計偏於不保守或過度保守之設計。;The analysis and design of conventional bridges to withstand seismic ground motions is based on the assumption that the ground motions over the entire foundation of the bridge are the same. However, the effects of temporal variation of earthquake ground motion do not be negligible for multiple-supp-orted bridges, and the excitation becomes a multiple-support excitation. The Vector Form Intrinsic Finite Element (VFIFE) is a new computational method and has the superior in managing the engineering problems with material non-linearity, discontinuity, large deformation and arbitrary rigid body motions of deformable bodies. In this study, VFIFE is adopted to analyze and compare the ultimate situation of the studied bridges with multiple-support excitation to uniform excitation. Two types of bridges, a fifiteen-span simply-supported bridge and a conti-nuous-span bridge with high-damping-rubber isolators are input four near-field ground motions to analyzed. Althrough numerical simulation of two bridges with uniform excitation or multiple-support excitation, the results show that the number of unseating decks of the simple-supported bridge with multiple-support excitation is larger than with uniform excitation. The continuous isolated bridge is subjected to multiple-support excitation, the number of unseating decks and thecollapse type are different from uniform excitation. But the collapse situation with multiple-support excitation is more than uniform excitation. The analysis indicates that the results of multiple-support excitation are different from the uniform excitation, and suggests using multiple-support excitation for the analy- sis and design of multiple-supported bridge.
