변형률에 따른 탄성계수 변화를 고려한 말뚝의 주면지지력 산정

Estimation of Pile Shaft Resistances with Elastic Modulus Depending on Strain

  • 김석중 (서울대학교 공과대학 건설환경공학부) ;
  • 김성헌 (서울대학교 공과대학 건설환경공학부) ;
  • 정성준 (서울대학교 공과대학 건설환경공학부) ;
  • 권오성 (대림산업(주) 기술연구소) ;
  • 김명모 (서울대학교 공과대학 건설환경공학부)
  • Kim, Seok-Jung (Dept. of Civil and Environmental Engineering, Seoul National University) ;
  • Kim, Sung-Heon (Dept. of Civil and Environmental Engineering, Seoul National University) ;
  • Jung, Sung-Jun (Dept. of Civil and Environmental Engineering, Seoul National University) ;
  • Kwon, Oh-Sung (Technology Research Institute, Daelim Industrial Co. Ltd.) ;
  • Kim, Myoung-Mo (Dept. of Civil and Environmental Engineering, Seoul National University)
  • 발행 : 2009.09.25

초록

Axial loads and shaft resistances can be calculated by load transfer analysis using strain data with load level. In load transfer analysis, the elastic modulus of concrete is a one of the most important parameters to consider. The elastic modulus, $E_{50}$, suggested by ACI (American Concrete Institute), has been commonly used. However, elastic modulus of concrete shows nonlinear stress-strain characteristic, so nonlinearity should be considered in load transfer analysis. In this paper, a load transfer analysis was performed by using data obtained from bi-directional pile load tests for four cases of drilled shafts. For consideration of nonlinearity, elastic modulus was calculated by both the Fellenius method and the nonlinear method, assuming the stress-strain relation of concrete to be a quadratic function, and then, the calculated elastic modulus was applied to the estimation of shaft resistance. The calculated shaft resistances were compared with the result obtained using the constant elastic modulus of ACI code. It was found that the f-w curves are similar to each method, and elastic modulus and shaft resistances decreased as strain increased. Moreover, shaft resistances estimated from elastic modulus considering nonlinearity were 5~15% different than those obtained using the constant elastic modulus.

키워드