Behaviour of steel plate girders with locally corroded WEB panels subjected to fires

Fire hazards are identified as one of the most critical threat to highway bridges worldwide. While these bridges are directly exposed to threats from vehicle induced hydrocarbon fires, the fact that most of the operating bridges are ageing would certainly accelerate the failure risk of bridges subjected to fires. This is because the aging would induce inevitable corrosion on bridge components resulting substantial material deterioration. Reported research showed that the steel plate girders are less fire resistant due to its high thermal conductivity and thermal expansion and it is equally vulnerable to corrosion when exposed to detrimental environmental conditions. Many corrosion problems have been reported in plate girder bridges in support regions due to their high tendency to stagnate moisture as a result of less air circulation. Web panels with local corrosion damage can reduce the shear buckling strength of the girders significantly. Current study investigates how the fire resistance of steel plate girders could be effected due to corrosion induced deterioration. A validated Finite Element (FE) model on the basis of heat transfer and coupled nonlinear thermo-mechanical analysis procedure was used to evaluate the fire resistance of a steel plate girder subjected to a shear dominant load. Temperature dependent thermal and mechanical properties of the material were modelled according to the EURO code recommendations. Most commonly encountered corrosion patterns reported in literature have been simulated using the FE model. ASTM E119 fire curve, which is used for the bridge fire modelling proposes, is used as the fire model with appropriate convection and radiation heat transfer coefficient. Results show a significant reduction of fire resistance in the deteriorated stage due to its reduction in shear capacity of the thin walled steel girders.