Size Effect on Flexural Compressive Strength of Reinforced Concrete Beams

철근콘크리트 보의 휨압축강도에 대한 크기효과

  • 김민수 (한국과학기술원 건설 및 환경공학과) ;
  • 김진근 (한국과학기술원 건설 및 환경공학과) ;
  • 이성태 (한국전력기술(주)) ;
  • 김장호 (세종대학교 토목환경공학과)
  • Published : 2002.12.01


It is important to consider the effect of member size when estimating the ultimate strength of a concrete flexural member because the strength always decreases with an increase of member size. In this study, the size effect of a reinforced concrete (RC) beam was experimentally investigated. For this purpose, a series of beam specimens subjected to four-point loading were tested. More specifically, three different effective depth (d$\approx$15, 30, and 60 cm) reinforced concrete beams were tested to investigate the size effect. The shear-span to depth ratio (a/d=3) and thickness (20 cm) of the specimens were kept constant where the size effect in out-of-plane direction is not considered. The test results are curve fitted using least square method (LSM) to obtain parameters for the modified size effect law (MSEL). The analysis results show that the flexural compressive strength and the ultimate strain decrease as the specimen size increases. In the future study, since $\beta_1$ value suggested by design code and ultimate strain change with specimen size variation, a more detailed analysis should be performed. Finally, parameters for MSEL are also suggested.


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