本文所要探討的彎曲薄壁箱型結構是由上、下環形板和內、外部殼所組成。除了考慮沿此箱型結構三主軸之位移與轉角外，也考慮沿此結構橫截面之翹曲(warping)效應。應用這些位移建立此箱型結構內各個應力合成量與應力偶合成量，進而計算其應變能及動能。接著應用漢彌爾頓原理建立結構的統御方程式，並以模態分析法求解此結構in-plane與out-of-plane的模態頻率值，及探討結構之幾何參數對於模態頻率之影響。並證明兩相異模態頻率所對應的模態形狀函數組具有正交性。最後分析結構承受一集中負載之動態響應行為。

　　The purpose of this study is to formulate the equations of motion for a curved thin-walled box structure with a closed rectangular cross-section. The structure is composed of the plate/shells elements.
　　An analytical method is presented to examine the free vibration for both the in-plane and out-of-plane motion of the box structure. Further, the orthogonality of any two distinct sets of mode shape functions for both types of motions of the structure is derived. The effects of different geometric parameters on the modal frequencies of both types of motions of the structures are investigated. The dynamic behavior of curved thin-walled box structure under the action of a transient load is also investigated.
　　Results show the first modal frequency for the in-plane motion decreases, however, the first modal frequency for the out-of-plane motion increases slightly as the radius of curvature increases. A transient load acted on the outer shell will induce both the in-plane motion and the out-of-plane motion of the structure. However, a transient load acted on the upper annular plate will induce the out-of-plane motion only of the structure.

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