한국지반공학회논문집 (Journal of the Korean Geotechnical Society)

  • 제35권6호
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  • Pages.5-15
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  • 2019
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  • 1229-2427(pISSN)
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  • 2288-646X(eISSN)
한국지반공학회 (Korean Geotechnical Society)
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국내 액상화 평가를 위한 진동전단응력비 산정

Evaluation Methods of Cyclic Shear Stress Ratio for the Assessment of Liquefaction in Korea

  • 유병수 (서울대학교 건설환경공학부) ;
  • 봉태호 (서울대학교 건설환경종합연구소) ;
  • 김성렬 (서울대학교 건설환경공학부)
  • Yoo, Byeong-Soo (Dept. of Civil & Environmental Eng., Seoul National Univ.) ;
  • Bong, Tae-Ho (Institute of Construction & Environmental Eng., Seoul National Univ.) ;
  • Kim, Sung-Ryul (Dept. of Civil & Environmental Eng., Seoul National Univ.)
  • 투고 : 2019.03.27
  • 심사 : 2019.05.08
  • 발행 : 2019.06.30
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초록

액상화 평가를 수행할 때 진동전단응력비(CSR)는 일반적으로 지반응답해석 또는 Seed & Idriss의 간편법을 수정한 방법을 통해 산정하고 있다. 본 연구에서는 진동전단응력비 산정방법의 적용성을 분석하기 위하여 1차원 등가선형 지반응답해석을 수행한 후 미연방도로국(FHWA), 일본도로협회(JRA), 국내설계기준(KDS) 등에서 제안한 방법을 적용하여 진동전단응력비를 산정하였다. 연구결과, 국내설계기준(KDS)으로 산정한 진동전단응력비가 해석 결과와 가장 큰 오차를 나타내었다. 그 이유는 국내설계기준의 경우 깊이에 따른 응력감소계수를 최대진동전단응력의 비가 아닌 최대지반가속도의 비로 정의하는 오류가 있기 때문이다.

Usually, the cyclic shear stress ratio (CSR) for the assessment of liquefaction has been determined by performing ground response analysis or adopting simplified method suggested by Seed & Idriss with some modifications. In order to analyze the applicability of the CSR evaluation methods, the present study performed one-dimensional equivalent linear analysis and evaluated CSR based on design codes from FHWA, JRA, and KDS. The comparison of the CSR obtained from each code showed that the CSR from KDS showed the largest error with the analysis results. The reason is because KDS has an error, which defines the stress reduction coefficient applying the maximum acceleration at each depth, not the maximum cyclic shear stress mobilized in the soil.

키워드

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Fig. 1. Analysis flow of one-dimensional equivalent linear ground response analysis

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Fig. 2. Evaluation of the maximum shear stress below a rigid soil mass

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Fig. 3. Ranges and average curve of stress reduction coefficient (Seed and Idriss, 1971)

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Fig. 4. SPT N value and Vs profiles at the study site

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Fig. 5. Normalized shear modulus and damping ratio curves adopted in the study

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Fig. 6. Response spectrum of input motions modified to match Korean Design Standard

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Fig. 7. Acceleration-time history of input motions

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Fig. 8. Comparison of stress reduction coefficients obtained from the present study

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Fig. 9. Comparison of CSR from each method

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Fig. 10. Conditions for calculating maximum shear stress

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Fig. 11. Comparison of the ratio of stress reduction coefficient

Table 1. summary of maximum and mean percent error for CSR

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