| Project/Area Number |
08650539
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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 |
土木材料・力学一般
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| Research Institution | KYUSHU-TOKAI UNIVERSITY |
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Principal Investigator |
SAKATA Yasunori Concrete Eng., Civil Eng., KYUSHU-TOKAI UNIVERSITY Professor, 工学部, 教授 (60099083)
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| Co-Investigator(Kenkyū-buntansha) |
OHTSU Masayasu Concrete Eng., Civil Eng., KYUSHU-TOKAI UNIVERSITY Professor(Kumamoto Univ.), 工学部, 教授 (80109016)
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| Project Period (FY) |
1996 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1998: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1997: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1996: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Keywords | Fatigue / Defect Inspection / Ultrasonic / Spectroscopy / Acoustic Emission(AE) / Spectral Responses / Deterioration / Earthquake Damage |
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| Research Abstract |
By using a grant-in-aid for scientific research from the Ministry of Education, Science, Sports and Culture, studies have been conducted on the above-mentioned title for three years. Fatigue deterioration of structures are classified into two cases. One is the deterioration due to large displacement and low cycle loading, such as earthquakes. The other case is gradual deterioration subjected to cyclic loading for a long time such as bridge. There exists a close relationship between deterioration and cyclic load level. Therefore, to evaluate safety and durability of structures, cyclic load level is an important factor to investigate deterioration of structure.
In this study, reinforced concrete (RC) beams under cyclic loading are investigated by the ultrasonic testing (UT) and the acoustic emission (AE). The cyclic load level is determined from the percentage to static bending strength of the beam. Amplitude of spectral response obtained from RC beam by the ultrasonic spectroscopy decrea
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se gradually with increase of load cycles. The amplitude show a tendency to decrease rapidly as higher as cyclic load level. Therefore, ultrasonic energy obtained by the spectral responses decrease with increase of load cycles. On the other hand, AE counts per unit time increase gradually according to increase of load cycles. The AE counts show a tendency to increase rapidly as higher as cyclic load level. The amplitude distributions of AF signal, are varied along with load cycles and cyclic load revel. The results show that spectral responses and AE count per unit time under fatigue process of RC beam could become an indicator of deterioration. Ultrasonic velocity also decrease with increase of load cycles. But variation of ultrasonic velocity is smoller than that of AE or spectral responses.
Theoretically, moment tensor analysis and SiGMA analysis for AE are developed by a co-investigator Ohtsu. Moment tensor analysis is used to classify AE events generated in concrete under loading. These methods are effective to clarify the fracture mechanism of the beam under cyclic loading. BEM analysis based on the visco-elastic theory is also performed using a model beam, and peak frequency and amplitude of spectral response are confirmed.
By combining together these results, it is confirmed to develop the inspection system to estimate deterioration of concrete structures suffered from earthquake damage and subjected to fatigue loading cycles. Less
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