等值靜力風載重於橋樑設計上的應用

Application of Equivalent Static Wind Loads on Bridge Design

王彬(Ping Wang)

指導教授 ： 林堉溢

淡江大學/工學院/土木工程學系碩士班/碩士(2013年)

https://doi.org/10.6846/TKU.2013.00226

摘要

國內已完成和正施工的懸索支撐橋樑數量日益增多，使得風載重在橋樑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繁瑣的工作。目前國內工程實務應用僅將風洞實驗結果當成橋樑設計之檢核。然而橋樑隨跨徑增長，風載重在橋樑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。
一般而言，動態反應可分為兩部分，背景部分及共振部分之反應。主要結構振態之共振部分抖振反應可根據抖振理論求得。背景部分之反應可以外力作用之分佈形式，或慣性力分佈形式表示。前者是以LRC法的概念求得，後者則是以類似於共振部分之方法求得。利用風洞實驗所得之資訊推導在設計風速下橋樑等值靜力風載重。以抖振理論將各振態反應分為共振及背景，再利用形狀函數、權重及尖峰因子，分別推導出各部份在設計風速下之等值靜力風載重，然後與平均風載重組合，可得到最大等值靜力風載重。
為了驗證方法的實用性，本文以簡支樑的結果與文獻做比較，得到相似的結果與分佈。並為了得知方法的實用性，以施工中斜張橋為例子。根據上述例子得出以下結論，以慣性力分佈之載重分佈情況相似於振態形狀，非實際載重之分佈情形，但兩種方法所得到的最大反應值相似，對於分析桿件內力而言，以慣性力分佈形式較為簡便，於工程設計上有一定的實用性。本文亦嘗試利用斷面模型實驗之反應結果產生等值靜力風載重，將反應頻譜分為共振部分及背景部分，分別計算兩部分之等值靜力風載重，使等值靜力風載重可直接由實驗結果得之。

關鍵字

等值靜力風載重 ； 橋樑設計 ； 抖振 ； 風洞實驗

並列摘要

The number of cable-supported bridges completed or under construction has been increasing in recent years. For this type of bridges, wind loads become significant and should be considered in 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 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 thesis, an approach to generate equivalent static wind loads at the design wind speed based on the information obtained from wind tunnel testing is proposed.
In general, the dynamic responses can be divided into two parts, namely, the background and the resonant responses. Based on the buffeting theory, the resonant part of the buffeting responses contributed by the major structural modes can be derived. The background responses can be expressed in terms of external wind load distribution or inertial load distribution. The former can be derived by using the concept of LRC, while the latter can be derived in a similar way to the resonant responses. Then using the weighting functions and peak factors, the equivalent static wind loads can be generated.
To examine the validity of the analytical approach, the results of a simply-supported beam were calculated and compared with those in the literature. The comparison indicates that the results are in good agreements. For demonstrating the applicability of this approach, an example of a cable-stayed bridge in construction was presented. By using this approach, the equivalent static wind loads can be generated and used for design in a combination with other loads.

並列關鍵字

Equivalent Static Wind Load ； Bridge Design ； Buffeting ； Wind tunnel test

參考文獻

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