土壤－結構互制效應對橋梁耐震評估之影響

The effect of soil-structure interaction on seismic assessments of briges

陳常麒(Chang-Chi Chen)

指導教授 ： 黃仲偉

中原大學/工學院/土木工程研究所/碩士(2014年)

https://doi.org/10.6840/CYCU.2014.00030

摘要

由於土壤與地下結構僅能提供有限的束制能力，因此橋墩底部的勁度會低於理想固接支承下的邊界條件。結構勁度的降低會導致基本振動週期變長，雖然所對應的譜加速度減少，但結構的位移亦將隨之增加，故土壤─結構互制對橋梁耐震評估的效應有待討論。本研究分別建立橋墩底端固接與考慮土壤─結構互制效應下之樁基礎與直接基礎等三種數值橋梁模型，後兩者以等效土壤彈簧模擬土壤─結構互制，利用非線性靜力側推分析探討考慮土壤─結構互制效應對橋梁耐震評估的影響，並比較靜力側推與動力歷時分析於考慮土壤─結構互制效應下之差異。其次，利用參數分析探討不同土壤、基樁埋深、直接基礎尺寸等對橋梁耐震評估的影響。模擬結果顯示理想固接支承會導致較保守的設計，而考慮土壤─結構互制效應可有效降低柱底的韌性比。

關鍵字

側推分析 ； 橋梁耐震評估 ； 直接基礎 ； 樁基礎 ； 土壤─結構互制

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. As a result, the bridge could be damaged due to large displacements. The effect of soil–structure interaction on the seismic assessment of bridges is studied in this study. Nonlinear static pushover analyses and dynamic time history analyses of single column bent bridges are performed by three separate types of finite element models. The first type model assumes that bridge columns are rigidly connected to the foundation while the second type model with pile foundation and the third type model with direct foundation both incorporate soil-structure interactions through the use of equivalent soil springs. In addition, parametric study is carried out to investigate the effects of soil types, buried depth of piles, and foundation sizes on the seismic assessments for bridges. Numerical results demonstrate that the fixed-end bridge designs will generate conservative results while the soil–structure interaction will effectively decrease the ductile ratio of the bridge columns.

並列關鍵字

Pushover analysis ； Seismic assessment ； Direct foundation ； Soil-structure interaction ； Pile foundation

參考文獻

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