| Project/Area Number |
09650633
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Building structures/materials
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| Research Institution | OITA UNIVERSITY |
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Principal Investigator |
SATO Yoshiaki OITA UNIVERSITY・FACULTY OF ENG. PROFESSOR, 工学部, 教授 (30038111)
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| Co-Investigator(Kenkyū-buntansha) |
KIYOHARA Chizuru OITA UNIVERSITY・FACULTY OF ENG. RESEARCH ASSOCIATE, 工学部, 助手 (00284787)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 1998: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1997: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Keywords | 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 / 乾燥開始材齢 / 圧縮フリープ |
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| Research Abstract |
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.
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