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Prediction of Shear Strength in High-Strength Concrete Beams without Web Reinforcement Considering Size Effect

크기효과를 고려한 복부보강이 없는 고강도 콘크리트 보의 전단강도 예측식의 제안

  • Bae, Young-Hoon (Research Institute of Construction Technology Kumho Eng.) ;
  • Yoon, Young-Soo (Dept. of Civil & Environmental Engineering, Korea University)
  • 배영훈 (금호엔지니어링 부설 건설기술연구소) ;
  • 윤영수 (고려대학교 토목환경공학과)
  • Published : 2003.12.01

Abstract

Recent research has indicated that the current ACI shear provision provides unconservative predictions for large slender beams and beams with low level of longitudinal reinforcement, and conservative results for deep beams. To modify some problems of ACI shear provision, ultimate shear strength equation considering size effect and arch action to compute shear strength in high-strength concrete beams without stirrups is presented in this research. Three basic equations, namely size reduction factor, rho factor, and arch action factor, are derived from crack band model of fracture mechanics, analysis of previous some shear equations for longitudinal reinforcement ratio, and concrete strut described as linear prism in strut-tie model deep beams. Constants of basic equations are determined using statistical analysis of previous shear testing data. To verify proposed shear equation for each variable, effective depth, longitudinal reinforcement ratio, concrete compressive strength and shear span-to-depth ratio, about 300 experimental data are used and proposed shear equation is compared with ACI 318-99 code, CEB-FIP Model code, Kim &Park's equation and Zsutty's equation. The proposed shear equation is not only simpler than other shear equations, it is but also shown to be economical predictions and reasonable safety margin. Hence proposed shear strength equation is expected to be applied to practical shear design.

최근의 연구를 통해서, ACI 전단 규준은 크기가 크고 인장철근비가 낮은 보에서 비보수적 예측을 보이는 반면 깊은 보에 대해서는 보수적 예측을 보임을 알 수 있다. 이러한 ACI 전단 규준이 가지고 있는 문제점을 수정하기 위해, 본 연구에서는 스터럽이 없는 고강도 철근 콘크리트 보의 전단강도 계산시 크기효과와 아치작용을 고려한 극한 전단강도 예측식을 제안하였다. ACI 전단 규준의 수정을 위해 포함될 항은 과학적 이론 및 분석에 근거한 $f_{sr}$ (dr), $f_{si}$ (${\rho}$)와 $f_{aa}$ (a/d)항이며, 선형 및 비선형 회귀분석을 통해 도출되었다. 기존의 실험 데이터 약 300여 개를 이용하여 각각의 변수에 대한 제안식의 검증 및 제안식과 ACI 318-99 code, CEB-FIP model code, Kim &Park 식 및 Zsutty 식과의 비교를 수행하였다. 제안식은 간단한 형태를 지니고 있지만, 경제적이면서도 합리적인 안전율을 확보할 수 있는 전단강도를 예측한다. 따라서 제안식은 실무에서 콘크리트 구조물의 전단설계에 적용 가능할 것으로 판단된다.

Keywords

References

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  1. Experimental Study of Reinforced High-Strength Concrete Beams without Stirrups Considering Shear Behaviour vol.14, pp.4, 2014, https://doi.org/10.5345/JKIBC.2014.14.4.336