考慮沖刷之樁基礎橋梁耐震評估

Seismic assessments for bridges with scoured pile foundations

莊哲宜(Che-Yi Chuang,)

指導教授 ： 黃仲偉

中原大學/工學院/土木工程研究所/碩士(2016年)

https://doi.org/10.6840/cycu201600080

摘要

一般工程設計與分析為簡化計算起見，皆假設橋墩固接於地面，然而實際上橋墩係透過不同的基礎型式將載重傳遞到地下。由於土壤僅能提供有限的束制能力，因此實際的勁度會低於理想固接支承下的邊界條件。本研究建立考慮土壤─結構互制效應的數值橋梁模型，利用等效土壤彈簧與阻尼模擬土壤─結構互制，並以分佈式塑鉸考慮基樁的非線性變形。分別利用非線性靜力側推與動力歷時分析探討土壤─結構互制效應對橋梁最大側向位移的影響，並比較兩種分析方式於考慮土壤─結構互制效應下之差異。其次，利用參數分析探討不同土壤與沖刷深度等對橋梁耐震評估的影響；最後，在考慮部分基礎裸露的狀況下，採用分佈塑鉸的方式模擬基樁的非線性變形，用以探討土壤─結構互制效應對基礎裸露橋梁耐震性能的影響。研究結果顯示撓曲勁度折減後之分佈式塑鉸所得結果與纖維元素所得結果相近，可用於工程實務上考慮土壤─結構互制的樁基礎橋梁靜力側推分析。同時對於軟弱土層而言，沖刷效應對橋梁的耐震性能有顯著的影響。

關鍵字

土壤─結構互制、等效土壤彈簧、樁基礎、分佈塑鉸、橋梁耐震評估

並列摘要

In most analyses and designs, bridge columns are assumed to be rigidly connected to the foundation. In reality, bridge columns, however, are buried into the ground with different foundations. Soil confinements provide limited stiffness which could elongate the natural period of the bridge and magnify the lateral displacements. The effect of soil–structure interaction on the seismic assessment of bridges is discussed in this study. Nonlinear static pushover analyses and dynamic time history analyses of single column bent bridges are performed to investigate the accuracy of the pushover analyses. The finite element bridge model incorporates soil-structure interactions through the use of equivalent soil springs and damping. In addition, parametric study is carried out to investigate the effects of soil types and buried depth of piles on the seismic assessments for bridges. Finally, distributed plastic hinges are adopted in piles to study the nonlinear deformation for piles due to the scouring of bridges. Numerical results demonstrate that the results from distributed plastic hinges with modified flexural stiffness coincided well with those from fiber elements in static pushover analyses. In addition, the scouring effects have significant effects on the seismic capacity for scoured bridges in soft soils.

並列關鍵字

Soil-structure interaction, Pile foundation, Distributed plastic hinges, Seismic assessment

參考文獻

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