Major accidents in industrial plants and storage sites may be triggered by seismic events, due to the damage of process equipment resulting in a loss of containment. A quantitative seismic risk analysis is used to demonstrate the risks (individual, societal, economic, and environmental) caused by an activity involving dangerous substances, in the case of earthquakes. Starting from the seismic hazard curve of the site in which the plant is placed, the risk is evaluated through the seismic vulnerability assessment of the equipment, generally expressed in terms of fragility curves. The risk calculation necessarily involves the effects of the content release from a critical unit (e.g., tanks, columns, etc...), which can provoke important effects on the surrounding elements and community. For each critical unit, a set of relevant failure modes and damage states associated with the release of material should be defined. While for steel storage tanks, these failure modes and relationship damage state/loss of containment are available and used, the same cannot be said for the other typologies of industrial equipment as columns, horizontal vessels, compressors, furnaces, etc... This paper aims to provide a criterion to determine damage states and loss of containment resulting from the structural seismic damage for different categories of industrial equipment. This problem has been solved in a deterministic way by introducing a “damage state/loss of containment” correlation matrices. The definition of these correlation matrices for the most critical types of equipment makes it possible to fill a gap that existed in the seismic risk evaluation procedure of an industrial plant, also allowing to evaluate the mean annual frequency of exceeding a certain loss of containment from a critical unit due to the earthquakes.

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