國內已完成和正施工的懸索支撐橋梁數量日益增多，使得風載重在橋梁設計上受到工程師更多的重視。然而在設計上使用包含靜力與動力的風載重仍是一複雜且煩瑣的工作。目前國內工程實務應用僅將風洞實驗結果當成橋梁設計之檢核。然而橋梁隨跨徑增長，風載重在橋梁設計上愈趨於掌控性的角色，因此設計時應將靜、動態風載重列入載重組合。本計畫的目的是利用風洞實驗所得之資訊推導在設計風速下橋梁等值靜力風載重，俾使橋梁工程師能以一相對簡易的方式將此載重融入設計上。橋梁的等值靜力風載重求取步驟與高層建築有所不同，在建築風洞實驗裡可用即時風壓量測得出風力歷時，然而在橋梁實驗上只能仰賴位移(或速度、加速度) 歷時資訊來取得振態反應。利用此振態反應結合橋梁抖振理論及LRC方法則可推導出在設計風速下對應於任一桿件最大內力之等值靜力風載重。本計畫裡將舉一斜張橋為例，來說明等值靜力風載重的應用及驗證此方法的可行性。 The increasing number of cable-supported bridges completed or under construction has attracted engineers’ attention to wind loads for bridge design. However, incorporating both static and dynamic wind loads for design use is still a tedious and difficult task. In current domestic engineering practice, wind tunnel testing (full aeroelastic model and/or section model) is used for confirmation only. Since wind loads play a more dominant role as bridge spans become longer, these loads should be taken into consideration in the design. In this project, an approach to generate equivalent static wind loads at the design wind speed based on the information obtained from wind tunnel testing will be proposed. The procedures for bridges are quite different from those for high-rise buildings in which instantaneous wind pressure measurements are possible. For bridges the major dynamic responses measured from wind tunnel tests are displacements (or velocities, accelerations) which will be used to retrieve modal characteristics. By using the information associated with buffeting theory and LRC concepts, equivalent static wind loads for the maximum internal forces on some critical members can be generated. An example of a cable-stayed bridge will be used to demonstrate the applicability of this approach.
