樁基礎受震行為之數值模擬

Numerical Analysis of Pile Behavior under Earthquake Loading

曾奕晨(I-Chen Tseng)

指導教授 ： 郭安妮

國立臺灣大學/工學院/土木工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.00832

摘要

為模擬地震作用下以及振動台試驗樁基礎的受側向力情況，本研究採用Boulanger等人於1999年所提出的方法，利用地盤反應分析得土層各深度的加速度歷時資料，再把加速度歷時轉換為位移歷時導入動態P-Y分析中，將樁基礎各深度的最大受力值與離心機試驗的結果作比較，結果極為相近。故本研究採用此方法模擬前述問題。
研究流程分三大部分，首先是加速度歷時資料之選取，第二步為地盤反應分析，最後將地盤反應分析後的加速度資料轉為位移歷時帶入動態P-Y分析中。在加速度資料選取我們採用台北盆地第一區設計反應譜帶入PEER ground motion database，系統自動找出50組與上傳反應譜最為相近的地震資料作為研究時的設計地震。地盤反應分析利用DEEPSOIL以擬線性頻率域分析將50組加速度資料。動態P-Y分析使用軟體OPENSEES利用Winkler beam為架構及O’Neill and Murchison在1983年發表的砂土P-Y曲線，將轉換後地盤反應分析位移歷時帶入即可得到樁基礎在該地震作用下的最大剪應力及彎矩。
分析案例為四組，分別是樁長為20m，樁長與地盤深度比值為1,2及3的案例A,B及C ;案例D樁長為10m，樁長與地盤深度比值為1。比較樁長度，深度比值與地震特性的影響。

關鍵字

地盤反應分析 ； DEEPSOIL ； 動態P-Y分析 ； OPENSEES

並列摘要

In the discipline of geotechnical earthquake engineering, the seismic behavior of pile can be analyzed by dynamic p-y method, or dynamic finite element / finite difference analysis. In this research, dynamic P-Y analysis, which is based on the theory of beam on nonlinear Winkler foundation (BNWF), is utilized to study the effect of input ground motion variability on pile response. In this study, before the dynamic P-Y analyses are performed, time history selection is carried out to select 50 recorded ground motions that are compatible with the target design spectrum of Taiwan Basin. Then, equivalent-linear frequency domain free-field site response analyses are performed (with the selected ground motions as input) to obtain the free-field displacement histories at various depths. These displacement histories are then imposed on the spring nodes in a dynamic P-Y analysis model.
Correlations between the computed pile response, in terms of maximum moment and shear force, and input ground motion parameters are studied. It is observed that the amplitude of the input ground motion (as represented by Arias Intensity, peak ground acceleration) has high correlation with pile response. Also, the correlation between frequency parameters of the input ground motion and pile response seems to be weak. However, the pile response seems to be higher if significant frequency of the input motion is close to the natural frequency of the pile. In addition, site-source distance or magnitude alone may not correlate well with the pile response, while input ground motion with shorter significant duration seems to lead to higher pile response.

並列關鍵字

Dynamic P-Y analysis ； OPENSEES ； ground motion variability ； site response

參考文獻

24.張暐承(2014)，「地盤反應與土壤液化之數值模擬研究」，國立台灣大學土木工程研究所，碩士論文。

23.賴泰辰(2014)，「中至高剪應變下混合土壤的動態參數」，國立台灣大學土木工程研究所，碩士論文。

30.凃亦俊 (2011)，「位於可液化砂土層中單樁基礎受震反應的離心模擬」，國立中央大學土木工程研究所，碩士論文。

15. Scott, R. F. (1981),“Foundation Analysis, Prentice-Hall International”, Inc., London, 267-334

8. Darendeli, M. B. (2001) "Development of a new family of normalized modulus reduction and material damping curves," Ph. D., University of Texas at Austin, Austin