Gallo, Marco (2024) Performance-based approach for bridges fire fragility assessment. [Tesi di dottorato]

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Abstract

This Ph.D. thesis, starting from an in-depth study of the scientific literature on fire engineering, proposes a methodological evolution in the field of performance approach for the assessment of fire vulnerability of infrastructure such as bridges and viaducts and subsequent retrofit. Criteria for assessing vulnerability to thermal and mechanical actions induced by fire events are standardized only in the case of buildings with specific uses. In addition, prescriptions are often lacking in performance-based approach, preferring verifications in prescriptive approach, which is easier to apply and provides conservative results. In the case of infrastructures, on the other hand, such criteria are not explicitly defined by the relevant technical standards although experience shows how the action due to fire can have impactful consequences on the functionality of the infrastructure. Referring to the relevant technical literature, one methodology was proposed by Kodur, that prescribes the performance criteria of infrastructures according to their “level of importance”. This thesis work extends the definition of the criteria by proposing four performance levels that the viaduct must satisfy according to its level of importance. The proposed approach aims at the utilization of Fire-Safety Engineering (FSE) principles by highlighting how this approach, although a higher computational burden, provides non-negligible performance differences. Finally, fragility curves are provided, using the Cloud linear regression method, based on different fire scenarios whose temperature curves were evaluated through a CFD analysis, for two levels of performance varying the static scheme and the initial utilization factor.

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