樁基礎沖刷橋梁模型之振動台實驗與分析研究

Numerical simulation of shaking table tests on dynamic response of a bridge model with scoured piled foundation

劉光晏(Kuang-Yen, Liu) ； 陳正鴻(Zheng-Hong, Chen) ； 陳家漢(Chia-Han Chen) ； 張國鎮(Kuo-Chun Chang)

《結構工程》 32卷2期 (2017/06) Pp. 108-130

https://doi.org/10.6849/SE.201706_32(2).0005

摘要

本研究提出土壤結構互制分析之簡化分析流程，探討樁基礎橋梁受地震與沖刷之複合式災害作用下之受震反應。土壤結構互制行為係以等效線性土壤彈簧模擬，主要特點為採用實測之土壤剪力波速與動態剪力模數來推估土壤彈簧之初始值，並假設樁身近域土壤與樁體產生相同剪力變形，根據地震作用下之土層有效剪應變對動態剪力模數進行修正，經少量迭代後獲致合理的等效線性土壤彈簧。此外，本研究建議地震時之土壤分層方式，根據白噪音訊號或者地震訊號作用下之土層加速度進行轉換函數，作為單層土及雙層土模型之依據。基於前述方法，本研究比較樁基礎沖刷橋梁模型之振動台實驗成果。分析結果顯示，無論在基樁有無裸露條件下，均能有效模擬上部結構之相對位移、絕對加速度，樁頂應變等之歷時與峰值，與沿樁長各高程之最大應變，且雙層土模型之預測結果均較單層土模型更佳準確。

關鍵字

振動台實驗 ； 樁基礎 ； 沖刷 ； 土壤彈簧

並列摘要

The simplified analysis process of soil-structure interaction is proposed in this research to study the response of the bridge with scoured piled foundation under earthquake. The simplified analysis applies soil spring to simulate soil-structure interaction behavior. Both soil shear wave velocity and dynamic shear modulus are used to estimate initial value of linear soil spring. Given two assumptions: (1) the shear strain of the soil near the pile is consistent to the strain of the pile, and (2) modification of dynamic shear modulus of soil follows the relationship of effective shear strain and maximum shear modulus, proposed by Seed and Idriss, the parameters of soil springs can be determined iteratively. Furthermore, a simplified approach to identify the soil layers subjected to seismic loading was also introduced by the predominant frequencies of soil layers by the transfer function analysis. Based on the proposed method, the SDOF bridge model with equivalent linear soil springs was built to simulate behavior of soil-pile-structure interaction in the shaking table test. The acceleration and relative displacement of superstructure, the strain of pile top, and the maximum strain of pile can be effectively predicted by the proposed method, either in the condition of exposed or no exposed pile foundation. In addition, the analyzed result of the model considering the double layers of soil can obtain better accuracy than that of the model with single layer of soil.

並列關鍵字

Shaking table test ； Pile foundation ； Scouring effect ； Soil springs