台灣混凝土變形預測模式B4-TW建置（一）：基本潛變、乾燥潛變與總潛變

Establishment of B4-TW Prediction Model for Concrete Deformation in Taiwan (I): Basic Creep, Drying Creep and Total Creep

10.6849/SE.201809_33(3).0003

劉庭愷(Ting-Kai Liu)；陳振川(Jenn-Chuan Chern)

混凝土 ； 長期變形 ； 潛變 ； 收縮 ； 資料庫 ； Concrete ； Long-term Deformation ； Creep ； Shrinkage ； Database

結構工程

33卷3期（2018 / 09 / 01）

43 - 64

繁體中文

台灣目前之混凝土工程設計規範缺乏混凝土潛變之預測公式，工程師設計大多依循美國ACI規範，參考美國AASHTO公路橋梁設計規範；歐洲CEB-FIP、RILEM；或日本JSCE、JCI等作法。基於台灣混凝土材料、配比、施工與環境之地區特性，台灣著實需要發展良好之本土化混凝土潛變預測公式。本文指出運用現有之國內外混凝土潛變模式預測台灣混凝土資料之情形，結果顯示大多現有模式皆呈現低估的現象。本研究評估並選用Bazant 2015年提出之Model B4潛變預測公式為基礎，針對上述之台灣混凝土特性進行本土化修正，分別是在瞬時應變項中考慮因粒料堅實度較為不足造成之混凝土彈性模數折減；在基本潛變項中考慮因高漿體量及粒料性質造成高變形之現象；在乾燥潛變項中考慮台灣常用之砂岩粒料造成之影響。結果顯示，進行本土化修正後之Model B4-TW潛變預測公式與原始Model B4相比，預測台灣混凝土基本潛變資料時，迴歸分析中之決定係數R^2由0.52提升至0.78；預測總潛變資料變形時R^2由0.76提升至0.81。除R^2外，各國學者提出之不同統計指標也顯示Model B4-TW預測台灣潛變資料之表現較佳，建議發展成為適用台灣本土之混凝土潛變預測公式。

At present the concrete design code in Taiwan lacks any predictive model for concrete creep, which is why most engineers in Taiwan follow the models of the American Concrete Institute (ACI) or the American Association of State Highway and Transportation Officials (AASHTO) of the US; the European CEB-FIP and RILEM; or the methods of the JSCE or JCI of Japan. Although the physical and chemical characteristics of concrete are essentially the same all across the world, each location uses its own constituent materials and mix design. In the present study, looking at the establishment of a concrete creep database for concrete in Taiwan, we have seen that the aggregate used in concrete of Taiwan is of lower quality. When formulating a mix design to attain higher strength, the resulting concrete will tend to have a high paste content, high cement content, low water cement ratio, and low aggregate/cement ratio. These local characteristics of concrete in Taiwan may lead to inaccuracies when they are applied to foreign predictive formulas, and in turn influence the structural behavior and safety of the concrete structures. Taiwan therefore has a manifest need for developing better localized predictive models for concrete creep. This study first presents the results from the predictive models for concrete creep (foreign and domestic formulas) applied to concrete in Taiwan. At present, it may be seen that the norms tend to undervalue. Then, it evaluates and actually uses the Model B4 predictive model for concrete creep suggested by Bazant in 2015 as a basis for the correction of characteristics in localized concrete in Taiwan in multiple situations: in instantaneous deformation items the reduction of the elasticity modulus in concrete due to low-quality aggregate was considered; in basic creep items the phenomenon of high levels of deformation due to high paste content and aggregate property were considered; in drying creep items the effect of sandstone aggregate, which is often used in Taiwan, was considered. Our results were as follows: after using the Model B4-TW model, which has been corrected for localized concrete in Taiwan, we may compare the two models (Model B4 and Model B4-TW); when predicting basic creep for Taiwan concrete, the coefficient of determination R^2 rose from 0.52 to 0.78; when predicting the total strain, R^2 rose from 0.76 to 0.81. In addition to R^2, the statistical indicators given by scholars from around the world have shown that the predictive capabilities of the Model B4-TW model for concrete creep data in Taiwan are superior to other models; thus it can be further developed as a predictive model for concrete creep in Taiwan.

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