The aim of this project is to benchmark the outcomes of a detailed performance based analysis using CFD and LS-DYNA software against codified methods used more generally on projects, and in particular to demonstrate whether this leads to an increase in the predicted capacity of the bridge under fire loading. The effect and influence of different parameters on the fire resistivity have been investigated. These are the location of the fire, the influence of different live loads, the influence of imperfections, the effect of wind fire interplay, and the effect of internal radiation between surfaces within a structural section. This research shows that doing a detailed thermal structural analysis of fire on a steel bridge can indeed lead to material savings. Performance based analyses show that the bridge does not fail for the considered fire scenarios for at least 30 minutes. When applying temperatures based on Eurocode, failure is reached after 15 minutes. Using a detailed FEM model to determine critical temperature results in four times less protection necessary than when the conservative Eurocode limit of 350 °C limit is used, a critical temperature of approximately 600 °C is found for the case study.