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Tensile Creep of Concrete at Early Ages

早期混凝土的拉伸徐变

基本信息

批准号：
09650509
负责人：
UMEHARA Hidetaka
金额：
$ 2.18万
依托单位：
Nagoya Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09650509/
关键词：
creep early aged concrete thermal stress creep strain 引張クリープクリープモデル

项目摘要

Creep behavior of concrete has been studied by many researchers, but almost all of them are concerned with matured concrete. This study has been conducted for prevention of cracking due to heat of hydration of cement in massive concrete. Compressive and tensile creep experiments have been carried out for early aged concrete such as from 1 day to 5 days. This study was focused on the influence of age of loading, stress-strength ratio, term of loading and temperature in curing and loading. The following results are obtained.(1) It was noted from compressive creep experiments that specific creep was constant with no influence by stress level below 50% of compressive strength, however, that specific creep significantly increased at over the value. And the influence of stress level and specific creep decreased corresponding to age of loading.(2) From tensile creep experiments it was cleared that the effect of the stress-strength ratio was significant and its relationship with creep strain could be described by an exponential equation. The age of loading influenced only the results of loading at 1 day, but little effect was observed in other age of loading. Aithouth the effect of curing temperature and term of loading could be assessed by equivalent periods of hydration, temperature effect during loading was much significant.(3) The method of modeling for change of stress has been investigated based on experimental results and applicability of super-positioning method for such stress has been assessed. It could be pointed out that a presented creep model which was modified Voigt model is applicable for early aged concrete and super- positioning method also could be applied for changing stress such as thermal stress.

混凝土的徐变行为已被许多研究者所研究，但几乎所有的研究都与成熟混凝土有关。为防止大体积混凝土中水泥水化热引起的裂缝，进行了这项研究。对早龄期混凝土进行了1d~5d的抗压徐变和抗拉徐变试验。重点研究了加载龄期、应力强度比、加载时间和温度对养护和加载的影响。结果表明：(1)压缩蠕变试验表明，在抗压强度为50%以下，比蠕变不受应力水平的影响，而当应力水平超过50%时，比蠕变显著增加。从拉伸蠕变试验可以看出，应力强度比的影响是显著的，其与蠕变应变的关系可以用指数方程来描述。加载年限只对第1天的加载结果有影响，而对其他加载年限的影响不大。虽然养护温度和加载时间的影响可以通过等效的水化周期来评估，但加载过程中的温度效应是非常显著的。(3)基于实验结果，研究了应力变化的建模方法，并对超位移法对这种应力变化的适用性进行了评估。指出在Voigt模型的基础上提出的徐变模型适用于早龄期混凝土，而超位移法同样适用于温度应力等应力的变化。