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PREDICTION OF DRYING SHRINKAGE CRACKING OCCURRED IN CONCRETE

混凝土干燥收缩开裂的预测

基本信息

批准号：
09650633
负责人：
SATO Yoshiaki
金额：
$ 1.98万
依托单位：
OITA 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 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09650633/
关键词：
Drying Shrinkage Cracking Drying Shrinkage Stress Analysis Compressive Creep Artificial Lightweight Aggregate Concrete Time of Occurrence of Cracking Tensile Strength Ratio Prediction of Cracking Finite Element Method 乾燥収縮応力 F.E.M解析乾燥

项目摘要

The purpose of this research project is to discuss the method for predicting the cracking due to drying shrinkage of concrete. The results of this study are summarized as follows :(1) The drying shrinkage cracking tests for normal and artificial lightweight aggregate concrete were performed according to JIS(draft), and the effects of the age at the start of drying on the cracking time were not recognized.(2) The tensile stress produced in the restraint concrete specimen was calculated by using the distribution of strain of the restraint steel, and the mean stress at the occurrence of cracking was 70 to 80 % of the tensile strength of concrete regardless of the age at the start of drying.(3) The artificial lightweight aggregate concrete was easy to crack compared with the normal concrete, and this is due to the amount of drying shrinkage strain ; the drying shrinkage strain of the artificial lightweight aggregate concrete was about twice that of the normal concrete.(4) The stress analysis system using the finite element method(F.E.M.) for the concrete laid in the dry air from early ages was developed, and the influence of the progress of cement hydration in the drying condition was considered in this system.(5) The stress distribution of concrete specimen was obtained by use of this stress analysis system, and the calculated stresses were compared with the tensile strength of concrete. The ratio of the stress to the tensile strength was called tensile strength ratio, and the area of the section where the tensile strength ratio was greater than 1.0 was obtained. The occurrence of the cracking was observed when the ratio of this area to the whole area reached 40 to 50 %. The proper criterion for the occurrence of cracking should be considered in the future.

本研究项目的目的是讨论预测混凝土干燥收缩引起的开裂的方法。本研究的结果概括如下：（1）根据JIS（草案）对普通和人造轻骨料混凝土进行干燥收缩开裂试验，未发现干燥开始时的龄期对开裂时间的影响。（2）利用约束钢的应变分布和出现时的平均应力计算约束混凝土试件中产生的拉应力。无论干燥开始时的龄期如何，开裂均为混凝土抗拉强度的70%至80%。（3）与普通混凝土相比，人造轻骨料混凝土容易开裂，这是由于干燥收缩应变的大小造成的；人造轻骨料混凝土的干燥收缩应变约为普通混凝土的两倍。(4)开发了针对早期在干燥空气中铺设的混凝土采用有限元法(F.E.M.)的应力分析系统，该系统考虑了干燥条件下水泥水化进程的影响。(5)利用该应力分析系统获得了混凝土试件的应力分布，将计算出的应力与混凝土的抗拉强度进行比较。应力与抗拉强度之比称为抗拉强度比，求出抗拉强度比大于1.0的截面面积。当该面积占总面积的比例达到40％至50％时，观察到裂纹的出现。将来应考虑裂纹发生的适当标准。