樁基礎縮尺橋梁模型之沖刷易損性曲線建置試驗研究

Experimental Study on Developing Scour Fragility Curves - A Case Study of Bridge Pile Foundation

沈明毅(Ming-Yi Shen)

指導教授 ： 張國鎮

國立臺灣大學/工學院/土木工程學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.02732

摘要

台灣受板塊擠壓之緣故，中央山脈橫亙於台灣本島中央，有著山高水急的地
形特色，於雨季時，龐大的降雨使得河川水位上升並快速流入海中，因有這樣的
地形與氣候環境，台灣的跨河橋梁普遍存在沖刷之現象，於颱風過境時橋梁倒塌
時有所聞。考量現行橋梁設計規範對受沖刷橋梁的不足，以可靠度分析方法修正
之，其中易損性曲線為不可或缺之一環，建立沖刷之易損性曲線有其必要性，本
研究將針對此議題進行探討。
本研究首先針對橋梁沖刷議題做資料收集及研究，了解其破壞模式與橋梁可
靠度分析等相關問題後，設計一系列之試驗，整理並歸納試驗之結果，提出一建
置沖刷易損性曲線之方法。橋梁沖刷是一複雜之流體、土壤、結構互制行為，本
研究針對土壤承載力破壞進行試驗探討橋梁結構行為，以及不同流況下橋梁沖刷
之發展情形，並觀察橋梁受沖刷之破壞機制。再以兩項實驗結果建立橋梁沖刷易
損性曲線方法，首先為樁基礎橋墩靜力承載試驗，以受不同沖刷深度之樁基礎側
推曲線，歸納實驗結果推論容量損失與沖刷深度之關係，以及縮尺橋梁模型水槽
實驗，收集橋梁受沖刷之各項參數，定義橋梁受沖刷之損壞指標，找出各損壞指
標所對應之沖刷指標，並控制環境因子，如流速、水位與載重配置等，其中實驗
之不確定性來自於土壤參數，重複多次實驗建立數據資料庫，以最大似然性法推
得沖刷指標之分布函數。最後結合兩個實驗之結果，修正沖刷指標，並建立沖刷
之易損性曲線。本研究建置沖刷易損性曲線之方法後，可供未來於可靠度分析與
設計上參考，考慮特定流域下，結合沖刷危害度曲線，推估橋梁因洪災所損壞之
機率。

關鍵字

橋梁沖刷 ； 易損性曲線 ； 最大似然性法

並列摘要

The escalating scale of natural disasters associated with global climate change and
the growing world population increasingly threatens civil infrastructure. In particular,
floods accelerate process of local scour around bridge piers resulting in damage to or
failure of cross-water bridge structures. This study proposed a procedure for
constructing scour fragility curves from flume experimental data for piled bridge pier.
By a series of single-pile bridge pushover tests, the relationship between scour
depth and capacity loss can be derived from the results. In addition, several flume
experiments with a pier model scouring under controlled conditions were conducted and
the scour process variation was observed. The scour depth observed from flume
experiments were used to develop scour fragility curve which could be applied to
evaluate the scour vulnerabilities of piled bridge pier for preliminary studies. A
methodology to construct the scour fragility curve from flume experimental data was
presented in this study; the main purpose of this paper is to show how the experimental
data were used to build the scour fragility curves which are defined as a function of
scour depth ratio or capacity loss ratio. The measured trend of the curves consists with
the general scour process and the realistic behavior of piled bridge pier damage
sequence. This paper has shown a feasible and practical methodology to construct the
scour fragility curves from experiments.

並列關鍵字

Bridge scour ； fragility curves ； the maximum likelihood method

參考文獻

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