Parametric fire curves for I-girder bridges submitted to under deck tanker fires

Abstract

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Bridge fires are of significant concern due to their potential consequences and the absence of standards for assessing fire resistance in bridges. The first step in this assessment involves building a fire model, often using Computational Fluid Dynamics (CFD) models. While CFD models are accurate, they are complex to build. This paper introduces closed-form expressions for parametric fire curves for I-girder bridges exposed to fires provoked by a burning tanker under the bridge mid-span or close to its abutments/piers. These fire curves eliminate the need for building CFD models and depend on key parameters defining the bridge (substructure configuration, width, span, vertical clearance) and the fire load (Heat Release Rate). The fire curves provide the adiabatic surface temperatures heating the bridge deck and their variation along the bridge deck longitudinal axis. The fire curves were obtained through a multi-step process that involved: a) a comprehensive design of experiments to define combinations of parameters used to build representative CFD models of I-girder bridges under fire, b) the use of ANOVA models to identify the most relevant parameters and parameter interactions, c) the use of multiple linear regression to derive the mathematical expressions, i.e. the fire curves, fitting the results of the CFD models run in the design of experiments step, d) a validation of the proposed fire curves for combinations of parameters not considered in the design of experiments. The resulting parametric fire curves are straightforward linear equations and can be easily generated with a spreadsheet provided as a Supplementary material. Consequently, these parametric fire curves represent a practical tool for both academics and practitioners interested in evaluating the fire resistance of I-girder bridges. This marks a significant step forward in enhancing bridge resilience against fire hazards.