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Study on the Evaluation of Influence of Creep on Autogenous Shrinkage Stress

蠕变对自收缩应力影响的评价研究

基本信息

批准号：
09650506
负责人：
MORIMOTO Hiroaki
金额：
$ 1.28万
依托单位：
Gifu University
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 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09650506/
关键词：
High strength concrete Autogenous shrinkage Young age Compressive creep Tensile creep Variable stress Method of superposition Effective Young's modulus 自己収縮

项目摘要

The following concepts were clarified on the compressive and tensile creep, the evaluation method of creep under changing stress and the calculation method of autogenous shrinkage stress of high strength concrete in early ages.1. Creep is proportion to a stress to the extent of 40 % of stress-strength ratio, at least.2. A significant difference is not recognized with compressive and tensile creep.3. Creep characterisitic changes greatly near by the age of 1 or 2 days, and the change is small after the age of 3 days.4. Basic creep function for high strength concrete in early age can be given by the product of final creep value and creep progress function.5. Creep value right after the stress reversal estimated by the method of superposition is grater than the measured a little, yet the estimated value generally agree well with the measured value.6. There are no remarkable differences between the estimated values by the time hardning rule and the strain hardning rule, and the estimated vales are fairly small compared with the measured value, especially right after the stress reversal.7. The time hardining rule and the time hardning rule require some appropriate correction considering the softning due to the stress reversal.8. The autogenous shrinkage stress of 1.5N/mmィイD12ィエD1 at the age of 7 days and 2.2N/mmィイD12ィエD1 at the age of 60 days were measured by using JCI method in high strength concrete having water-cement ratio of 30%.9. The autogenous shrinkage stress can be estimated by the increment method using the effective Young's modulus calculated from measured creep coefficient of high strength concrete having water-cement ratio of 30%.10. The Young's modulus reduction coefficient for calculation of autogenous shirinkage stress is a little smaller than that for thermal stress calculation

阐明了高强混凝土早期抗压、抗拉徐变、变应力下徐变的评价方法和自收缩应力的计算方法。蠕变与应力的比例至少为应力强度比的40%。压缩蠕变和拉伸蠕变没有显著差异。1、2日龄前后蠕变特性变化较大，3日龄后变化较小。高强混凝土早期基本徐变函数可由徐变终值与徐变进程函数乘积给出。用叠加法估计的应力反转后的蠕变值略大于实测值，但与实测值基本吻合。时间硬化法和应变硬化法的估计值之间没有显著差异，与实测值相比，估计值很小，尤其是在应力逆转后。考虑到应力逆转引起的软化，时间硬化规则和时间硬化规则需要进行适当的修正。采用JCI法测定了水灰比为30%的高强混凝土在龄期为1.5N/mm D12 D1和龄期为2.2N/mm D12 D1的自收缩应力。采用水灰比为30%的高强混凝土蠕变系数计算有效杨氏模量，采用增量法估算自收缩应力。计算自缩应力时杨氏模量折减系数略小于计算热应力时的杨氏模量折减系数