沉箱頂版之非線性分析

Abstract

摘要 本論文以有限元素法針對沉箱頂版作非線性分析之研究，主要探討以實際橋樑設計的沉箱頂版，作為分析的模型。假設模型尺寸為固定且以垂直荷載及梯形荷載型式之位移作用於墩柱斷面上，利用變換墩柱斷面尺寸，即改變剪跨-深度比，研究其極限承載強度-變形之響影性。 程式分析結果顯示，在同樣沉箱頂版尺寸下，墩柱面積(即荷載面積)愈大，剪跨-深比將愈小，其極限承載力就愈大，達極限載重的變位量將愈小。經由本研究的結果可得知現行撓曲設計公式所計算沉箱頂版的極限承載力遠小於ACI 318-02 code以基礎版之貫穿剪力、深樑之壓拉桿模式的估算公式或DIANA程式分析的結果。沉箱頂版若以撓曲方法設計將略嫌保守，因此在舊有橋樑的修補工程，可以此作為參考及分析後再判斷是否有補強之必要。

Abstract In this thesis, the finite element method was adopted for non-linear analyses of a cover plate of caisson. The size of the cover plate of caisson is assumed to be constant. The ultimate bearing capcity of cover plate and load-deflection relationship were investigated under vertical and trapezoid loading by displacement with different column size,i.e., shear-span to depth ratios. The shear-span to depth ratios decrease as the size of the pier column , loading area, increased , under the same size of the cover plate of caisson.The results of FE-analysis show that the deflection in the loading surface reduces and bearing capcity of cover plate increases as shear-span to depth ratio decreases under ultimate loading. The ultimate bearing capcity of the cover plate of caisson calculated by the current flexure design formulas is less than that calculated by the ACI 318-02 code formulas based on punching shear, the strut-and-tie model for deep beam, and the results of DIANA program analyses. According to design of the current flexure formulas, the cover plate of caisson is too conservative. It is not necessary to be strength for cover plate due to the improvement of the design code.