Journal of Korean Society of Coastal and Ocean Engineers (한국해안·해양공학회논문집)

Korean Society of Coastal and Ocean Engineers (한국해안·해양공학회)
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Development of Time-Dependent Reliability-Based Design Method Based on Stochastic Process on Caisson Sliding of Vertical Breakwater

직립방파제의 케이슨 활동에 대한 확률과정에 기반한 시간의존 신뢰성 설계법 개발

  • Kim, Seung-Woo (Department of Civil and Environmental Engineering, Seoul National University) ;
  • Cheon, Sehyeon (Department of Civil and Environmental Engineering, Seoul National University) ;
  • Suh, Kyung-Duck (Department of Civil and Environmental Engineering, Seoul National University)
  • 김승우 (서울대학교 건설환경공학부) ;
  • 천세현 (서울대학교 건설환경공학부) ;
  • 서경덕 (서울대학교 건설환경공학부)
  • Received : 2012.06.11
  • Accepted : 2012.09.12
  • Published : 2012.10.31
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Abstract

Although the existing performance-based design method for the vertical breakwater evaluates an average sliding distance during an arbitrary time, it does not calculate the probability of the first occurrence of an event exceeding an allowable sliding distance(i.e. the first-passage probability). Designers need information about the probability that the structure is damaged for the first time for not only design but also maintenance and operation of the structure. Therefore, in this study, a time-dependent reliability design method based on a stochastic process is developed to evaluate the first-passage probability of caisson sliding. Caisson sliding can be formulated by the Poisson spike process because both occurrence time and intensity of severe waves causing caisson sliding are random processes. The occurrence rate of severe waves is expressed as a function of the distribution function of sliding distance and mean occurrence rate of severe waves. These values simulated by a performance-based design method are expressed as multivariate regression functions of design variables. As a result, because the distribution function of sliding distance and the mean occurrence rate of severe waves are expressed as functions of significant wave height, caisson width, and water depth, the first-passage probability of caisson sliding can be easily evaluated.

직립 케이슨 방파제에 대한 기존의 성능설계법은 임의의 시간 동안의 평균활동량을 산정하지만 허용활동량을 최초로 초과하는 사건의 발생확률(최초통과확률)은 계산하지 못한다. 설계자는 구조물이 최초로 피해를 입을 확률에 대한 정보를 구조물의 설계 단계뿐 아니라 관리 및 운영에서도 필요로 한다. 따라서 본 연구에서는 케이슨 활동의 최초통과확률을 산정하기 위해 확률과정에 기반한 시간의존 신뢰성 설계법을 개발하였다. 방파제의 활동을 일으키는 폭풍파는 발생 시간과 강도의 임의성의 특징이 있기 때문에 Poisson spike process를 사용하여 케이슨 활동을 정식화할 수 있다. 여기서 방파제의 활동을 일으키는 폭풍파의 발생률은 활동량분포함수와 폭풍파의 평균발생률로 표현된다. 성능설계법으로 모의된 이들은 설계변수들의 다변량 회귀함수로 나타내진다. 결과적으로 활동량분포함수와 폭풍파의 평균발생률은 유의파고, 케이슨 폭, 수심의 함수로 표현되어 케이슨 활동에 대한 최초통과확률을 손쉽게 산정할 수 있다.

Keywords

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Cited by

  1. Evaluation of Allowable Criteria in First-Passage Probability Method for Caisson Sliding of Vertical Breakwater vol.25, pp.5, 2013, https://doi.org/10.9765/KSCOE.2013.25.5.317
  2. Reliability Analysis of the Long Caisson Breakwater Considering to the Wave Force Reduction Parameter vol.29, pp.2, 2017, https://doi.org/10.9765/KSCOE.2017.29.2.121