Post-fire analysis and numerical modeling of a fire-damaged concrete bridge

Extreme fire hazard is not a typical design consideration for highway bridges because of the low probability of occurrence. However, historically, fire events caused higher numbers of bridge collapse than earthquakes on the nation’s highways, showing the criticality of fires on highway bridges. Despite this fact, the during and post-fire performance of highway bridges is still not well-understood. The current study evaluated the post-fire performance of a fire-damaged concrete bridge in Irving, Texas, through theoretical modeling and in-situ testing. The bridge sustained significant damage when a fuel tanker crashed and caught fire in May 2005, and was then repaired and strengthened with carbon fiber reinforced polymer laminates. A three-tiered calibrated numerical modeling scheme involving computational fluid dynamics-based fire model, heat transfer and stress analysis was developed. The accuracy of the scheme was validated through static bridge load testing. It was found that the modulus of elasticity of the fire damaged section of the bridge was reduced by more than 50%. The numerical model represented the bridge fire with reasonable accuracy. The model thermal profiles showed good correlation with actual post-fire observations. The concrete modulus of elasticity decreased by 10% and 75% for the girder and the deck, respectively. The actual strain and displacements from the load testing closely matched those from the calibrated model.