2015-08-012024-05-17https://scholars.lib.ntu.edu.tw/handle/123456789/695719摘要：擴展式基腳是橋梁在堅實地盤場合常使用的基礎型式，一般情況下係以承受垂直載重為主，但當上部結構同時承受水平力作用時，如地震慣性力等，基腳將因彎矩作用而產生旋轉變位，致使上部結構傾斜，甚至發生穩定問題，係設計時所要檢核的主要項目之一。一般耐震設計原則係以橋柱之塑性彎矩強度為基礎設計力，在此設計力作用下，擴展式基腳之偏心距1/3（50%接觸面積）之傾覆檢核規定常控制設計結果，並使所設計之基腳尺寸過大。實際上，當基腳允許偏心距達1/3，其基盤會因基礎上揚而具有相當程度柔性，加上在地震作用下基礎之搖擺反應，整體上結構所受之慣性力會降低，使得原本預期會在橋柱產生之塑鉸機構不見得會發生。因此，近年來有許多研究者嘗試考量上述基礎搖擺機制，降低地震需求，以期得到更合理經濟之設計結果。為使基礎搖擺消能機制落實於耐震設計中，本研究針對橋梁擴展式基腳，研究其在地震作用下之搖擺反應，並發展適合工程設計使用之分析方法，如反應譜法、容量震譜法及動力歷時分析法等，以供後續發展考量基礎搖機制之耐震設計法使用。<br> Abstract: Spread footings are a commonly used foundation type for bridges on firm ground. They are generally subjected to vertical loading, but when their superstructure is subjected to horizontal loading, such as seismic loading, they may have rotational displacements due to moments at the column base. The rotational displacement may tilt the structure and even make it become unstable. Therefore, the moment capacity is one of major design item for spread footings. The current seismic design principle is capacity design to use the column plastic moment as the foundation design load for preventing the foundation from damage during earthquakes. A design requirement of the footing eccentricity of less than 1/3 usually governs the design results and leads to too large size of footing. When the eccentricity of a footing reaches 1/3, the column base will become quite flexible due to the foundation uplift, and the footing rocks under earthquakes, which will reduce the inertial forces on the structure. In this way, the originally expected column plastic hinge mechanism may no longer happen. Therefore, in recent years, many researchers attempted to consider the above rocking behavior in seismic design to have a smaller seismic demand and therefore have more economic and reasonable design. To implement the rocking mechanism in seismic design, this study is going to investigate the rocking behavior of bridge spread footings under seismic loading and develops appropriate analysis methods, such as the spectrum method, capacity spectrum method and dynamic time history analysis method, for the use in seismic design.淺基礎擴展式基腳搖擺基礎耐震設計Shallow foundationsSpread footingsRocking foundationSeismic design.