橋梁下部載重耐震設計與防災之研究

Abstract

摘 要 在國內從事橋梁設計，必須引用的法令依據是「公路橋梁設計規範」及「公路橋梁耐震設計規範」，以下簡稱【規範】。而這兩種國內法規是參考AASHTO規範及1960年版日本橋道路橋示方書，以下簡稱【橋示】而編訂的。本研究著重在比較【規範】與【橋示】規定的荷載下，對於結構物所產生之剪力與力矩大小作一比較研究。再利用鑽探所取得的資料對地盤種類的判別，以及已知固定周期公式來決定水平震度係數Kh值，並同時引用上述兩種規範，自行舉例加以計算分析，以補充本國【規範】對水平震度係數Kh值計算資料的不足。 對於因為車輛超載，而產生橋面破裂現象，【規範】規定計算輪重時必須增加30%外，橋面厚度須維持20公分，梁的中心距應≦260公分，但【橋示】自阪神大地震後對於載重設計也作了大幅修正，本研究中對於【規範】與【橋示】規定的載重作一比較分析，發現應用【橋示】規定的載重時，計算梁的力矩與剪力值大於應用【規範】規定的載重，計算梁的力矩與剪力值。此外對於橋梁下部結構而言，針對傳統設計法及耐震設計法做一比較，以最作為設計時的參考。本文另外對橋基保固方面也提出對傳統力學觀點不同的經驗，以為將來橋梁下部結構設計時，能一併考慮將橋基保固設計納入防災體係，使橋梁防災系統有更宏觀的作法。

Abstract It was necessary to quote the rules from [Road & Bridge Design Code] and [Road & Bridge seismic Design Code] (quoted “Codes”) for bridge design in our country. Those two codes were consulted with [AASHTO Code] and [Bridge & Road Design Book & Solutions in Japan, 1960] (quoted “Solutions”) for formulation. Our study focused more on comparison of the rules of truck-loading under “Codes” and “Solutions” with the measurements of value M (Moment of Force) and value S (Share of Force) affected to the infrastructure. Then, this study would use the raw data from boring through the judgment of the classification of stratum, as well as use already-known formulation of period function (T) to determine the horizontal seismic force coefficient (value Kh). In the meantime, it quoted the information in those two codes (“Solutions”) together with some examples made by this study to calculate and analyze the database of value Kh in order to compensate the insufficient calculation-data of the value Kh in “Codes”. Because of overloading of vehicle, it would cause breaking joint on the bridge. Therefore, the “Codes” set up rules to deal with those problems. First, it had to increase another 30% of loading when calculated the wheel loading. Second, thickness of bridge floor had to maintain 20 cm. Third, center-to-center of beam had to be 260 cm. On the other hand, the “Solutions” made some major amendments on the design of loading after the Kobe earthquake. This study compared the rule of loading in “Codes” with the rule in “Solutions”. It was found that the application of truck-loading in “Solutions” to calculate the value M and value S of the beam were larger than the application of truck-loading in “Codes” to calculate the value M and value S of the beam. In addition, for the reference of final design, this study also compared the traditional design with the seismic design to substructure. Besides, different experiences on protection of bridge foundation have been raised in this study in comparison with the traditional mechanics. It’s better to consider containing hazard mitigation system with bridge foundation protection together when designing the bridge substructure in the future. It would make the system of bridge hazard mitigation more spaciously and contractively.