現今大地工程中，性能設計法的應用與日漸增，其相關研究益趨頻繁。目前大地工程性能設計規範以歐盟Eurocode和日本Geo-Code21為代表。本研究擬藉採以性能設計法中的可靠度分析法 (Reliability analysis) 探討樁基礎的耐震性能特性，本研究的分析工具為一維波動方程(EQWEAP)，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。本研究在地震考量上，係根據中央氣象局定義之地震震度分級表，選擇震度四級(中震)至震度七級(劇震)之地震震度作為一選取範圍，另根據台灣地震危害度曲線顯示，台北地區之回歸週期1年與2500年地震的地表最大加速度分別為0.03g與0.51g，將上述加速度值設定為最大與最小地震值，並搭配有限差分法計算不同地震於同一設計年限下之發生機率，而地盤的參數設定上為求研究簡化，皆採以標準常態分佈進行設計。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，並將其結果與PBEE分析作一比較。研究以台北新莊地區快速道路橋梁樁基礎 (樁徑為2m) 為例，透過蒙地卡羅法與一階可靠度分別求取數值模型於不同耐震性能等級下之可靠度指數，研究發現：蒙地卡羅的可靠度指數範圍為(2.0~6.0)略大於一階可靠度的可靠度指數範圍(2.0~4.8)，但兩種分析結果的整體趨勢皆顯示該橋梁樁基設計能滿足建築耐震設計要求，耐震性能II和耐震性能III下均滿足韌性容量和不斷樁之要求，唯獨於耐震性能I下，其可靠度指數小於目標可靠度指數。此現象與PBEE分析結果相似。本研究亦根據研究結果制定在不同地震震度發生時，其橋梁樁基礎應滿足之耐震性能。 This study intends to discuss the applications of reliability analysis on seismic performance of pile with one-dimensional wave-equation modeling EQWEAP. Numerical examples were conducted for typical pile foundations on a bridged expressway located at Sinjhuang District in New Taipei City. Nonlinear moment-curvature relation of the concrete pile was used to simulate the damages and failure of the piles. In this study, the pile foundation is designed as 3×3 piles with pile diameter of 2m and length of 60m. The area ratio of steel bar is about 1.94%. The pile is only applied with the vertical load of 18000kN. For Reliability analysis of the time-dependent behavior of the pile, selected seismic records were adjusted to different PGAs (0.03g~0.51g) as the input motions. The corresponding weights of these scenarios were calculated and multiplied with the number of failures to compute for the reliability index. The assessments were based on the internal bending moments recorded at the interface between pile and the pile cap. Three seismic levels were considered with the critical moment capacities of the pile. The computed reliability indexes for MCS are 2.0~6.0, and those for FORM are 2.0~4.8. For seismic level I, the piles will be slightly damaged and the cracks will occur at the pile head. Nevertheless the most pile shaft will remain elastic. For seismic level II, the maximum bending moment occurred at the pile head would cause the bar to yield but no plastic hinge was found. For seismic level III, the piles were found safe without fully mobilizing the ultimate moment. The results are similar to the previous findings using the PBEE analysis. According to the calculations, the reliability index of MCS is bigger than FORM analysis, the details of the comparison require more studies.
