基樁承載力之可靠度分析及載重阻抗因子初步研究

Preliminary Study on Reliability Analysis and Load Resistance Factors for Pile Capacity

凃嘉翔(Chia-Hsiang Tu)

指導教授 ： 張德文

淡江大學/工學院/土木工程學系碩士班/碩士(2009年)

https://doi.org/10.6846/TKU.2009.00459

摘要

本研究目的是將可靠度的觀念應用於樁基礎設計上，採用一階可靠度法對於台北盆地之場鑄基樁及麥寮之PC樁進行承載力之可靠度分析。主要有兩個主題:（1）使用一階可靠度法來分析基樁在不同承載力推估公式時，其安全係數與破壞機率的關係。（2）載重阻抗係數設計法（LRFD）於基樁設計之應用，並對阻抗折減因子及載重因子之值做初步的建議。
研究結論包括：（1）基樁可靠度分析結果:場鑄樁與PC樁之可靠度分析結果，皆屬於安全之設計。（2）安全係數之建議值:不論何種推估方法由於Chin氏詮釋法之詮釋結果會有高估之現象，故其建議安全係數皆相對較低。（3）參數變異性:樁徑、修正係數、貫入試驗N值對於場鑄樁會有所影響，而土壤單位重、不排水剪力強度、有效摩擦角並無明顯之影響。樁徑、不排水剪力強度、修正係數、貫入試驗N值對於PC樁樁會有所影響，而土壤單位重、有效摩擦角並無明顯之影響。（4）阻抗折減因子及載重因子之值做初步的建議：於四種推估方法中，阻抗係數及活載重係數均隨著載重比增加而增加，而靜載重係數則隨著增加而些微降低，方法A及方法B分別為 =1.011~1.122及 =1.021~1.099；而 =1.057~1.519及 =1.054~1.575； =0.225~0.490及 =0.290~0.491。而PC樁之載重及阻抗因子，方法C及方法D之分別為 =1.021~1.097及 =1.021~1.095；而 =1.058~1.502及 =1.054~1.492； =0.298~0.463及 =0.248~0.436

關鍵字

承載力 ； 可靠度分析 ； 破壞機率 ； 載重及阻抗因子設計

並列摘要

In this study, a reliability approach,the First Order Reliability Method (FORM), is used to analyze the reliability of the ultimate capacity of cast-in-place piles in Taipei basin and driven piles in Me-Liao . Two tasks conducted in this study are:（1）using the First Order Reliability Method (FORM) to analyze the relationship between the safety factor and the probability of overestimation ,（2）application of the Load and Resistant Factor Design（LRFD）method on pile design, and some preliminary suggestions are made on the value of resistance reduction factor and load factors.
Major conclusions are drawn as follows:（1）the analytical results of pile: the analytical results of cast-in-place piles in Taipei basin and driven piles in Me-Liao is over conservative design.（2）suggestions of the safety factor: whatever formulas for pile capacity estimation is studied, the results of Interpretation Method for Chin is overhigh, so suggestions of the safety factor is lower.（3）the variation of parameter: Pile diameter、revision factor and SPT-N value had some effect for cast-in-place piles . Unit weigh、undrained shear strength and effective friction angle had no effect distinctly for cast-in-place piles. Pile diameter、undrained shear strength、revision factor and SPT-N value had some effect for driven piles . Unit weight and effective friction angle had no effect distinctly for driven piles.（4）some preliminary suggestions are made on the value of resistance reduction factor and load factors: for using four kinds of formulas for pile capacity estimation, resistance factor and live load factors will increase when the ratio of live load to dead load is increased, and resistance factor and dead load factors will reduce when the ratio of live load to dead load is increased.Method A and method B are =1.011~1.122 and =1.021~1.099； =1.057~1.519 and =1.054~1.575； =0.225~0.490 and =0.290~0.491. Method C and method D for the Load and Resistant Factor of the driven piles are =1.021~1.097 and =1.021~1.095； =1.058~1.502 and =1.054~1.492； =0.298~0.463 and =0.248~0.436.

並列關鍵字

axial capacity ； reliability analysis ； failure probability ； load and resistance factor design

參考文獻

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