樁基礎耐震性能之研究

機構典藏 > College of Engineering > Graduate Institute & Department of Civil Engineering > Thesis > Item 987654321/87835

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Title:	樁基礎耐震性能之研究
Other Titles:	Study on seismic performance of pile foundations under earthquakes
Authors:	王寅綸;Wang, Yin-Lun
Contributors:	淡江大學土木工程學系碩士班張德文;Chang, Der-Wen
Keywords:	樁基礎;波動方程;樁受震行為;性能分析;PBD;EQWEAP;pile foundation;wave equation analysis;damage model;equivalent foundation stiffness;seismic performance
Date:	2013
Issue Date:	2013-04-13 11:47:33 (UTC+8)
Abstract:	近年來，性能設計法應用和相關研究益趨頻繁。眾所周知，現有之大地工程性能設計規範以歐盟Eurocode和日本Geo-Code21為代表。本研究擬藉由美國太平洋地震工程研究中心所建議的機率分析法 (PBEE analysis) 探討樁基耐震性能特性，所採用的數值工具為一維EQWEAP分析，該分析係結合集中質塊法、孔隙水壓模式及波動方程式方法等研發而成，具簡易快速特性。另根據台灣地震危害度曲線顯示，台北地區之回歸週期30年、475年和2500年地震的地表最大加速度分別為0.12g、0.29g和0.51g，上述加速度值將成為耐震性能評估重點。除地盤的非線性行為外，基樁的非線性行為亦屬重要，本研究係以LPILE程式推算基樁彎矩容量，界定性能狀態標準，以討論不同耐震性能目標下樁身最大位移和彎矩影響。研究結果顯示：上述分析可充分瞭解樁基在地震下行為，包括：基樁反應 (最大位移、彎矩和剪力分布、瞬間最大變形和內力分布)、不同地震等級下之基樁位移和彎矩性能 (也即IM-EDP、λ-EDP、DM-EDP、λ-DM關聯性)，進而做為評估其耐震性能使用。研究以台北新莊地區快速道路橋梁樁基礎 (樁徑為2m) 為例，嘗試數值模型的耐震性能以及相關參數所造成的影響，研究發現：該橋梁樁基大致能滿足建築耐震設計要求，除在中小地震下，樁頂部位似有開裂之虞外；設計地震和最大考量地震下均滿足耐震性能韌性容量和不斷樁要求。長樁可減少樁身內力，故可提升其耐震性能；硬地盤基樁將較軟地盤基樁抗震性能為高。此外，地盤運動決定基樁的運動方式，地震力大小遠較地盤之土壤變異性重要，大口徑樁的樁頂和樁底位移相對較小 (本研究<10cm)，可忽略二次彎矩影響，上構慣性力不宜以靜態力模擬，其將導致過份保守結果。在較大地震下，工址地盤或有局部液化現象，惟對大口徑樁影響有限。樁頂韌性容量提升應為設計者努力方向，本研究另建議基樁耐震性能評估流程供實務應用參考。 This study intends to discuss the applications of probability analysis on seismic performance of piles with the one-dimensional wave-equation modeling. Numerical examples were conducted for typical pile foundations on a bridged expressway located at Sinjhuang District in New Taipei City. From the local seismic hazard curves, peak ground accelerations at the moderate, the design and the maximum consideration earthquakes were targeted, and the seismic records were created based on the significance of past quakes. Nonlinear moment-curvature relation of the concrete pile was used to simulate the damages and failure of the piles. For a typical pile foundation where each pile has a diameter of 2m and the area ratio of steel bar about 1.94%, if the vertical load is 9000~18000kN and a horizontal force approximates from 0~2700kN, the maximum pile displacements under different design levels were found roughly at 19, 45 and 79 cm for a 60m longer pile. Presuming a fixed head condition, the piles will be slightly damaged and the cracks will occur at the pile head due to the moderate quakes. Nevertheless the most pile shaft will remain elastic. For the design earthquake, the maximum bending moment occurred at the pile head would cause the bar to yield but no plastic hinge was found. For maximum consideration earthquake, the piles were found safe without fully mobilizing the ultimate moment. The results can be used for the assessments of the seismic design for these foundations. A design procedure is suggested comparing the maximum bending moment of the pile under the earthquake with the moment capacities of the pile.
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