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1993 Fiscal Year Final Research Report Summary

Fracture Mechanics of High Strength Concrete and Size Effect

Research Project

Project/Area Number 04650510
Research Category

Grant-in-Aid for General Scientific Research (C)

Allocation TypeSingle-year Grants
Research Field Building structures/materials
Research InstitutionTohoku University

Principal Investigator

MIHASHI Hirozo  Tohoku Univ., Dept. of Architecture, Assoc. Prof., 工学部, 助教授 (90091751)

Co-Investigator(Kenkyū-buntansha) NARITA Takeshi  Tohoku Electric Power Co., Research Institute, Res. Eng., 技術研究所, 主任研究員
NUMAO Tatsuya  Tohoku Univ., Dept. of Urban and Civil Eng., Assoc. Prof., 工学部, 助教授 (90164649)
KIRIKOSHI Kazuki  Tohoku Univ., Dept. of Architecture, Tech. Ass., 工学部, 教務技官 (60240660)
SOMURA Noriaki  Tohoku Univ., Dept. of Architecture, Res. Assoc., 工学部, 助手 (80125632)
Project Period (FY) 1992 – 1993
KeywordsHigh Strength Concrete / Fracture Mechanics of Concrete / Size Effect / Tension Softening / Microstructure / Brittleness Index / Steel Fiber Reinforced Concrete
Research Abstract

Crack resistance and size effect in high strength concrete were studied from the view point of fracture mechanics of concrete. The following results were obtained.
1) Although fracture energy of concrete increases up to about 80MPa of the compressive strength, it turns to decrease beyound 100MPa of the compressive strength when RILEM standard notched beams of 100x100x8400 (mm) were used. On the other hand, wedge splitting compact tension specimens with a six times larger size give a higher values of the fracture energy than that of notched beams even for the very high strength concrete of about 100MPa.
To investigate the mechanism to couse the difference, the changing rates of tangential stiffness load-CMOD curves were analyzed. It was shown that the fracture process zone in front of the crack tip was fully developed before the fracture in large specimens but not in smaller ones.
2) While high strength concrete is realized by making the microstructure finer, it changes strongly the tension softening properties and especially increases the maximum cohesive stress. It was clarified that the maximum cohesive stress is empirically described as a function of the porosity.
3) Brittle index defined with three parameters determined by standard tests, can well charcterize the crack resistance properties of concrete with various strength and sizes of specimens.
4) Steel fiber reinforcement provides high strength concrete with higher crack resistance.

  • Research Products

    (8 results)

All Other

All Publications (8 results)

  • [Publications] H.Mihashi: "How to Predict Size Effect in Concrete Structures" Preprints of Size Effect in Concrete Structures. 235-246 (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 中村裕: "各種鋼繊維を用いた鋼繊維補強コンクリートの破壊挙動及び軟化特性に関する実験的研究" 東北大学建築学報. 33. 39-50 (1994)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 中村裕: "コンクリートの高強度化及び寸法の増大による脆性化機構に関する実験的研究" 日本建築学会東北支部研究報告集. 57(印刷中). (1994)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 中村裕: "コンクリートの高強度化が寸法効果に及ぼす影響に関する研究" 日本建築学会学術講演梗概集. A(発表予定). (1994)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] H.Mihashi and N.Nomura: "How to Predict Size Effect in Concrete Structures" Proc. of JCI International Workshop on Size Effect in Concrete Structures. 235-246 (1993)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] H.Nakamura, H.Mihashi, K.Kirikoshi, K.Hirai: "Fracture Behavior and Tension Softening Diagram in Fiber Reinforced Concrete (in Japanese)" The Architectural Reports of the Tohoku University. No.33. 39-49 (1994)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] H.Nakamura, H.MIhashi, K.Kirikoshi and K.Hirai: "Experimental Study on the Brittle Behavior of Concrete Influenced by Material Structures and the Size of Specimens" Proc. of Tohoku Branch Meeting of Artitectural Institute of Japan (in Japanese). Vol.57 (in press).

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] H.Nakamura, H.Mihashi and K.Kirikoshi: "Size Effect in High Strength Concrete (in Japanese)" Proc. of Annual Meeting of Architectural Institute of Japan. Vol.A (to be published). (1994)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1995-03-27  

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