| Project/Area Number |
10450203
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | Nagoya Institute of Technology |
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Principal Investigator |
ICHINOSE Toshikatsu Nagoya Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (10151474)
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| Project Period (FY) |
1998 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥10,100,000 (Direct Cost: ¥10,100,000)
Fiscal Year 2001: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2000: ¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1999: ¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 1998: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Keywords | Reinforced concrete / scale effect / rib shape / bond strength / cover thickness / splice / fracture mechanics / stirrups / 強度算定式 / 鉄筋径 / 全数継手 / 異形鉄筋 / 付着破壊 / 剛体バネモデル / ひび割れ / エポキシ樹脂 / ブラックライト / CTスキャン |
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| Research Abstract |
There is a current interest in using large bars for reinforcing in seismically resistant structures to both reduce congestion and maintain clear spacing between them. While a larger amount of experimental and analytical works have been carried out to study the effects of scale on the shear strength and flexural strength of reinforced concrete, relatively less attention has been devoted to the effects of scale on the bond strength of reinforcement including the effects of scale on tension lap splice strength. This issue has become important for the seismic resistant design of lap splices because the use of small diameter bars leads to congestion and splitting bond failure under strong earthquake loadings.
This work is to investigate the effects of scale, rib-shape and lateral reinforcement on bond strength between deformed bar and concrete using pullout and lap splice tests. The specimen parameters are three kinds of bar diameter, two kinds of rib shape, cover thickness, and with/without stirrups. From experimental results, the following conclusions are obtained: 1) pullout specimens with smallest cover thickness showed the largest scale-effect; 2) larger confinement by either cover concrete or stirrups resulted in smaller scale-effect; and 3) scale-effect is attributable to brittle splitting crack around deformed bars and not to local crushing of concrete in front of ribs. Finite element analyzes are also conducted considering the fracture mechanics theory. Based on the experimental and analytical results, design equations are proposed for lap splice. The equations yield large scale-effect for splice with small cover and short splice length where brittle behavior is expected. On the other hand, the equations yield small scale-effect for bars with lower rib height and many stirrups where ductile behavior is expected. The proposed equations agree with the existing experimental results.
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