|摘要: || 長跨徑人行拱橋近年來深受工程師青睞，此型橋梁除滿足交通需求外，更能扮演當地景觀地標角色。因人行橋面版窄大多採用單拱設計，由於單拱缺乏側向支撐，拱順風向之氣動力反應也越趨明顯。而傳統斜張橋或懸索橋氣動力分析只考慮橋面版風力，因此無法適用於拱橋上。所以本研究建立一數值分析模式，以主梁斷面及橋拱斷面之顫振導數及風力係數為基礎，推導整體橋梁顫振與抖振理論。並採用兩例題，分別為單面吊索及雙面吊索拱橋，利用所推導之數值分析模式，配合橋拱斷面實驗求得之實驗數據進行顫振與抖振分析，來探討加入橋拱氣動力參數對整體顫振臨界風速與抖振位移反應影響。|
The long-span arch bridges have been a favorable choice for the design of pedestrian bridges during the past decades in Taiwan. This is because the type of bridges not only can satisfy the transportation needs but also may become the landmark in the local area. In these pedestrian bridges, a single arch is the only choice due to the narrow bridge deck. Since the single arch lacks lateral support and its height increases with the bridge span length, the drag responses in the arch become significant and cannot be negligible. To predict the aerodynamic responses of the arch, the traditional analysis used for cable-stayed and suspension bridges, considering wind forces acting on bridge decks only, cannot be used. In this thesis, an analytical approach based on flutter and buffeting theory associated with the information measured from section model tests is presented. Two examples are used to demonstrate the validity and applicability of this approach and to investigate the effects of the forces acting on the arch on the flutter wind speed and buffeting responses of bridge decks.
The results show that the critical flutter wind speeds in these two examples are dominated by the flutter derivatives of bridge decks. The increases of the critical flutter wind speeds considering flutter derivatives of arches are less than 1%. For the buffeting responses, the effects of the forces acting on arches are significant on both drag and torsional responses of arches and bridge decks. In Example 1 incorporating forces acting on the arch into the analysis, the drag and torsional responses of the bridge deck increase 1.9% and 44.1%, respectively. The increases of the drag and torsional responses of the arch are 764% and 792%, respectively. Since the structural coupling between the bridge deck and the arch is minor in this example, the main contribution to the responses of the arch is the forces acting on the arch itself. Therefore, the results with huge increases are expected. In Example 2 incorporating forces acting on the arch into the analysis, the drag and torsional responses of the bridge deck increase 11.99% and 133%, respectively. The increases of the drag and torsional responses of the arch are 57.87% and 64.6%, respectively. In this example, the structural coupling between the bridge deck and the arch is more obvious than in example 1. The effects of the forces acting on the arch on the responses of the arch and the bridge deck are significant. From the results stated above, the forces acting on the arch should be considered in the analysis.