隔震橋梁藉由隔震系統延長結構物自然振動週期，以降低引致之地震力。傳統隔震橋梁主要採用隔震支承系統，當隔震支承橋梁之工址地質優良時，其基礎可同時採用直接基礎，大地震時，直接基礎可能發生搖擺現象。本研究進行一系列振動台實驗，探討隔震橋梁採用直接基礎時，搖擺效應對於整體橋梁動力反應之影響。試驗結果發現，隔震支承橋梁之直接基礎發生搖擺時，橋面板與橋墩頂位移皆增加，但可更進一步降低橋墩之內力，顯示直接基礎搖擺亦有隔震效果。 本研究亦採用有限元素方法，建立一座五跨連續梁橋，探討直接基礎搖擺對隔震支承橋梁之動力反應影響，再進一步探討基礎大小如何影響搖擺效果，及其造成之橋梁整體反應不同。分析結果可發現，隔震橋梁採用直接基礎，於大地震下，發生基礎搖擺，降低橋梁引致之地震力，使橋墩仍保持在彈性狀態，進而降低橋柱韌性需求。 ;The mechanism of isolated bridges is mainly by using the isolator to prolong the structural period to reduce the seismic force. However, for those bridges located in stable soil condition site can also be designed by use the spread foundation, which can reduce the seismic force of the main structure by rocking response, under the extreme earthquake. The aim of this study is to discuss the dynamic response of isolated bridge considering the rocking mechanism of spread foundations by doing a series of shaking table tests. Experiments show that the displacement of both deck and top of pier increase under the rocking effect of foundation, but the internal force of the pier decrease. This result gives the proof that the rocking mechanism can also provide the isolation effect. The finite element method is also adopted in this study to simulate the dynamic behaviour of the isolated bridges under different size of spread foundations. The target bridge is a five-span continuous bridge, simulation results show that the foundational rocking increases the feasibility, and the pier can also maintain in the elastic behavior, furthermore, the required strength and ductility of the pier can be decreased.
