An integrated modelling framework for complex systems safety analysis

Abstract

The ever-increasing complexity of engineering systems has fuelled the need for novel and efficient computational tools able to enhance the accuracy of current modelling strategies for industrial systems. Indeed, traditional Fault and Event Tree techniques still monopolize the reliability analysis of complex systems despite their limitations, such as the inability to capture underlying dependencies between components or to include degradation processes and complex maintenance strategies into the analysis. However, the lack of alternative solutions able to tackle large-scale modelling efficiently has contributed to the continued use of such methodologies, together with their robustness and familiarity well rooted in engineering practice. The current paper defines a novel modelling framework for safety system performance which retains the capabilities of both fault and event tree methods, but also overcomes their limitations. The ambition is to provide a technique for application to realworld systems preserving a familiar user-model interface and grounding the novel approach in well-known and established reliability techniques. In order to describe the methodology developed and demonstrate its validity, five casestudies referring to a simplified industrial plant cooling system are analysed and discussed. Further discussion regarding the scalability of the proposed approach is provided, outlining the advantages of the current implementation and its computational cost.

Reliability assessment of man‐machine systems subject to probabilistic common cause errors

“…To analyze the deterministic relationships between risk factors, the subtasks in the ET are regarded as top events in the FT 19 . By identifying the different types of risk factors (including machine failures, environmental disturbances and HEs) that can lead to the failure of the top event, the logical relationships between risk factors and subtasks can be described using a logical link function (e.g., AND/OR gate) in the FT 31,32 …”

“…The success or failure of the subtasks will influence the evolutionary path of the system. To analyze the deterministic relationships between risk factors, the subtasks in the ET are regarded as top events in the FT. 19 By identifying the different types of risk factors (including machine failures, environmental disturbances and HEs) that can lead to the failure of the top event, the logical relationships between risk factors and subtasks can be described using a logical link function (e.g., AND/OR gate) in the FT. 31,32 Currently, many studies have utilized the ET-FT method for risk assessment of systems. 33 Targoutzidis 34 utilized the ET-FT method to incorporate human factors into the risk assessment of workplaces.…”

A Nested Petri Net -- Fault Tree Approach for System Dependency Modelling

“…The Dynamic and Dependent Tree Theory (D 2 T 2 ) [Andrews and Tolo (2023)] was designed to overcome such limitations and offer a more realistic modelling of system behaviour through the integration of traditional Fault and Event Tree with more flexible techniques such as Petri Nets and Markov Models. These are applied to the modelling of dependencies or complex behaviour (e.g., non-standard maintenance models, dynamic features) of individual components, and the information obtained reintroduced in the initial Fault Tree model in order to proceed with its computation [Tolo and Andrews (2022)]. However, in real-world applications, dependencies often involve entire subsets of components rather than individual ones: this may imply the construction of large Petri Nets or Markov Models representing individual components dependencies and may result challenging for the analysts.…”