Although Fault Tree and Event Tree analysis are still today the standard approach to system safety analysis for many engineering sectors, these techniques lack the capabilities of fully capturing the realistic, dynamic behaviour of complex systems, which results in a dense network of dependencies at any level, i.e. between components, trains of components or subsystems. While these limitations are well recognised across both industry and academia, the shortage of alternative tools able to tackle such challenges while retaining the computational feasibility of the analysis keeps fuelling the long-lived success of Fault Tree and Event Tree modelling. Analysts and regulators often rely on the use of conservative assumptions to mitigate the effect of oversimplifications associated with the use of such techniques. However, this results in the analysis output to be characterised by an unknown level of conservatism, with potential consequences on market competitiveness (i.e., over-conservatism) or safety (i.e., under-conservatism). This study proposes a generalization of the Dynamic and Dependent Tree Theory, which offers theoretical tools for the systematic integration of dependency modelling within the traditional Fault and Event Tree analysis framework. This is achieved by marrying the traditional combinatorial nature of failure analysis, formalised by the Fault and Event Tree language, with more flexible modelling solutions, which provide the flexibility required to capture complex system features. The main advantage of the proposed approach in comparison to existent solutions is the ability to take into account, under the same modelling framework, any type of dependency regardless of its nature and location, while retaining the familiarity and effectiveness of traditional safety modelling.

翻译：尽管故障树与事件树分析至今仍是许多工程领域系统安全分析的标准方法，但这些技术缺乏完整捕捉复杂系统真实动态行为的能力，导致在任意层面（即组件之间、组件序列之间或子系统之间）形成密集的依赖网络。虽然这些局限性在工业界和学术界已得到广泛认知，但由于缺乏既能应对此类挑战又能保持分析计算可行性的替代工具，故障树与事件树建模得以长期保持其成功地位。分析师和监管机构通常依赖保守假设来缓解因使用此类技术导致的过度简化问题。然而，这会导致分析结果带有未知程度的保守性，可能对市场竞争力（即过度保守）或安全性（即保守不足）产生潜在影响。本研究提出了动态依赖树理论的泛化框架，该框架为在传统故障树与事件树分析体系内系统集成依赖建模提供了理论工具。通过将故障树与事件树语言形式化的传统失效分析组合特性，与更具灵活性的建模方案相结合，实现了捕捉复杂系统特征所需的建模灵活性。与现有方案相比，所提方法的主要优势在于能够在同一建模框架下考虑任何性质与位置的依赖关系，同时保持传统安全建模方法的熟悉度与有效性。