應用台灣收縮與潛變預測公式於長跨距預力混凝土橋梁及拱壩壩體長期分析

Application of Shrinkage and Creep Prediction Model of Concrete in Taiwan to Prestressed Concrete Bridge and Dam in Long-term Analysis

高健鈞(Jian-Jyun Gao)

指導教授 ： 廖文正

國立臺灣大學/工學院/土木工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202102332

摘要

臺灣的RC結構設計大多只依據強度與耐震性能為考量，而忽略收縮與潛變所造成的耐久性影響，如此不僅錯估使用年限，可能會由於結構老化造成結構安全及使用性的疑慮。以臺灣為例，由於本土粒料性質的特性，收縮與潛變通常都較國外預測來的大，像臺北地區重要的交通要道圓山橋，在達到使用年限之前橋跨中央就發生過大的垂直變位，嚴重影響橋梁的使用性，由此可凸顯修正混凝土收縮與潛變行為的重要性。
黃禾程曾於2020年透過Python與數值分析，參考Model B4回歸出一套專屬臺灣的收縮與潛變預測公式Model B4 TW (2020)，此公式考量眾多混凝土參數，完整反映收縮與潛變複雜的混凝土行為，但公式本身還是於材料層面的預測，還未進一步詳細模擬於真實結構上，其工程之應用面還未得到研究探討。
故本研究首先就Model B4 TW (2020)進行參數敏感度之分析，對各項參數於應變的影響作更深入的探討，利用Python的隨機種子與3D視覺的方式進行參數敏感度，利用較簡易的概念得到各項參數對於收縮潛變的敏感度，此結果將可於工程上快速得知如何於配比設計階段考量混凝土的收縮與潛變量。
而後，為探討公式於結構上的適用性，本研究選用國道一號五股至楊梅段之預力混凝土橋梁為研究案例，其原因為此橋梁工程有珍貴的長期垂直變位監測資料，故結合現在業界常用的MIDAS Civil建模進行分析，同時以Model B4 TW (2020)與各國不同的規範為收縮潛變之變數，比較公式所預測之變位與真實情況的差異，進而探討本土化公式在結構層面的適用性。
在進行完預力橋梁的分析探討後，本研究選用拱壩為研究案例，水庫貴為民生重要建設，其水資源更是影響數百萬的人民生活，而壩體因長期受外力影響，因此亦受潛變變形影響，然而在舊有的水庫及時變位評析系統中並未融入混凝土潛變行為的概念，只關注於溫度與水位變化的影響，因此本研究以翡翠水庫為研究案例，建立ABAQUS有限元素模型，詳細探討溫度、水位、潛變對於壩體變位的影響，並探討其應力應變之分析，利用模型分析觀察壩體的安全性，希望在日後對於水庫的安全管理改善以及警戒值的訂定有初步之探討。

關鍵字

混凝土 ； 收縮 ； 潛變 ； 參數敏感度分析 ； 預力橋梁 ； 拱壩

並列摘要

Most RC structural design in Taiwan was mainly focused on strength and seismic performance, while ignoring the potential durability issues induced by shrinkage and creep. This not only incorrectly estimates the service life, but also cause safety and serviceability concerns due to structural aging. In Taiwan, due to the characteristics of local aggregate materials, shrinkage and creep are usually higher than those predicted by international models. The notable deflection of the Yuanshan Bridge caused by underestimated shrinkage and creep are observed and seriously affects its serviceability, which reminds the importance of revising the shrinkage and creep behavior of concrete.
In 2020, Python and numerical analysis was used by Ho-Cheng Huang to revise a set of Taiwan-specific shrinkage and creep prediction formula Model B4 TW (2020) mainly modified based on Model B4. This model considers many parameters and fully reflects the shrinkage and creep. However, Model B4-TW is still at the material phase, and has not been further verified on real structures, and its engineering application has not been studied and discussed.
Therefore, this research first conducts the parameters sensitivity analysis of Model B4 TW. Python's random seeds and 3D vision to perform parameters sensitivity analysis were applied, which is easier to understand the concept of derives the sensitivity of various parameters to shrinkage and creep.
Then, in order to explore the applicability of the model to the structure, the prestressed concrete bridge from WuYang Highway was chosen as the research case by implementing B4-TW in MIDAS Civil. The reason is that the long-term monitoring deflection data are available, and the simulation results by Model B4 TW (2020) and different prediction models are further compared.
After analyzing and discussing the prestressed bridge, the arch dam was also selected as a research case. The arch dam is also affected by external forces for a long time, but creep behavior was not well considered into the previous reservoir displacement evaluation system and only focused on the influence of temperature and water level changes. Therefore, Feitsui Reservoir was selected as a research case and finite element analysis by ABAQUS was conducted for the influences of temperature, water level, and creep on the displacement of the dam. The stress and strain analysis was also carried out to evaluate the safety of the dam, and to improve the safety management and alertness of the reservoir as well.

並列關鍵字

Concrete ； Shrinkage ； Creep ； Model B4 TW (2020) ； Parameters sensitivity analysis ； Prestressed concrete bridge ； Arch dam

參考文獻

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[3] Holt, E., and M. Leivo, 2004, “Cracking Risks Associated with Early Age Shrinkage,” Cement and Concrete Composites, 26.

[4] Davis, H.E.,1940, “Autogenous Volume Change of Concrete,” ASTM, PP.1103-1113

[5] De Larrard., and Roy, L.R, “Creep and Shrinkage of High Performance Concrete,” Proc. of the 5th Int. RILEM Symposium on Creep and Shrinkage of Concrete, Barcelona, Spain, PP.499-504, 1993.