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Research Paper

Seismic Fragility Analysis for a Gas-Plant System using Fault Tree-based Bayesian Network

고장수목 기반 베이지안 네트워크를 이용한 가스 플랜트 시스템 지진 취약도 분석

Se-Hyeok Lee1*
,
Sangki Park2
,
Jeong-Rae Cho3
이 세혁1*
,
박 상기2
,
조 정래3
1Senior Researcher, Department of Structural Engineering Research, Korea Institute of Civil Engineering and Building Technology, Goyang, 10223, Korea
2Research Fellow, Department of Structural Engineering Research, Korea Institute of Civil Engineering and Building Technology, Goyang, 10223, Korea
3Senior Research Fellow, Department of Structural Engineering Research, Korea Institute of Civil Engineering and Building Technology, Goyang, 10223, Korea
1한국건설기술연구원 구조연구본부 수석연구원
2한국건설기술연구원 구조연구본부 연구위원
3한국건설기술연구원 구조연구본부 선임연구위원
*Corresponding Author
31 August 2025. pp. 237-246
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Abstract

A fault tree-based Bayesian network (FT-BN) framework was proposed for the seismic probabilistic safety assessment (sPSA) of gas plants. The framework models the components of a system as random variables, and constructs a network based on the correlations derived from plant processes. The constructed BN demonstrates strong potential for making risk-informed decisions when different types of information are available. However, performing sPSA for plant systems requires detailed fragility data for individual components, which remains limited in existing literature. To address this gap, a literature review was conducted, revealing that the Hazus Earthquake Model Technical Manual (2024) developed by the Federal Emergency Management Agency (FEMA) provides fragility curves for entire systems as well as for individual plant equipment. The objective of this research is to validate that the FT-BN can derive system-level fragility from component-level fragilities and to compare the resulting system fragility with that provided by FEMA. To achieve this, several hypothetical plot-plans were assumed, and corresponding FT-BNs were constructed. Numerical investigations confirmed that the system fragilities estimated using the FT-BN were generally more conservative than those presented by FEMA. These findings suggest that the FT-BN framework enables a more comprehensive assessment by incorporating the unique characteristics of each system.

Keywords
fault tree
bayesian network
probabilistic safety assessment
system fragility
gas plant

확률론적 지진 안전성 평가(Probabilistic Safety Assessment)를 위해서 고장수목(Fault Tree) 기반 베이지안 네트워크(Bayesian Network, BN) 방법론이 제안된 바 있다. 해당 방법론은 시스템 구성요소들을 확률변수로 가정하고 변수들의 상관관계를 네트워크로 구축한 후, 변수들에 다양한 정보들을 입력함으로써 유연한 시스템 의사결정 수행이 가능하다는 장점이 있다. 그런데 이러한 시스템 평가를 위해서는 개별 요소들의 취약도 정보는 필수적이나, 플랜트 관련 설비들의 취약도 정보는 매우 한정적이다. 따라서, 우선적으로 문헌조사를 수행하였고 Federal Emergency Management Agency(FEMA)에서 전체 시스템과 더불어 다양한 구조물 및 설비들의 취약도 정보를 제공함을 확인하였다. 본 연구에서는 FEMA에서 제공하는 시스템 취약도와 개별 요소들의 취약도 정보를 기반으로 BN을 통해 도출한 시스템 취약도를 비교･분석하는 것을 목표로 한다. 이를 위해 세 규모의 가스플랜트 Plot Plan을 정의하였고, 이에 대응하는 BN 모델을 이용하여 시스템 취약도를 산출하였다. 세 규모에 대해 도출한 시스템 취약도와 FEMA에서 제공한 시스템 취약도를 비교한 결과, 도출된 취약도가 보수적으로 산정됨을 확인하였고, 추가적으로 구축된 BN의 개별 설비들의 취약도 손상 상태(Damage State, DS)를 변경해가면서 시스템 취약도를 산출한 결과 역시 FEMA에서 제시한 값보다 보수적임을 확인하였다. 이는 시스템의 고장을 정의하는 DS 차이로 인한 결과이며 플랜트마다 모델링을 기반으로 하는 시스템 취약도 산출이 필요한 것으로 이해할 수 있다.

키워드
고장 수목
베이지안 네트워크
확률론적 안전성 평가
시스템 취약도
가스 플랜트
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Information
  • Publisher :Computational Structural Engineering Institute of Korea
  • Publisher(Ko) :한국전산구조공학회
  • Journal Title :Journal of the Computational Structural Engineering Institute of Korea
  • Journal Title(Ko) :한국전산구조공학회 논문집
  • Volume : 38
  • No :4
  • Pages :237-246
  • Received Date : 2025-04-17
  • Revised Date : 2025-05-09
  • Accepted Date : 2025-05-09
  • DOI :https://doi.org/10.7734/COSEIK.2025.38.4.237
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