Bridges, Tunnels and other Transportation Structures
Full Session with Abstracts
Fire events on bridges have caused greater economic damage than seismic events, and it is also one of the least understood of common extreme events. Bridge infrastructures subjected to different types of fire can catastrophically collapse or be heavily damaged due to thermal effects. External wrapping of damaged concrete bridge components with Fiber Reinforced Polymer (FRP) laminates has been used as a strengthening technique for fire damaged bridges. There is a lack of knowledge on the long-term performance and structural integrity of fire damaged and FRP strengthened bridges. One such rare in-service bridge, more than 50 years old in Irving, Texas, was selected for this study. Two columns, three girders and one pier cap were damaged when a fuel tanker crashed and caught fire in May 2005. The fire damaged cast-in-place non-prestressed girders were subsequently repaired with mortar and strengthened with carbon FRP (CFRP) laminates. The girders were instrumented with strain gauges and displacement transducers, and a non-destructive live load test was carried out, 12 years after the FRP strengthening. The results from the load test were used to evaluate the performance and determine the lateral flexural load distribution. The fire-damaged strengthened girder exhibited a midspan deflection about 20 percent higher than the undamaged girder. The effect of fire was modeled using Fire Dynamic Simulator (FDS) to accurately estimate the post-fire material properties of the girder and deck. The fire model and heat transfer analysis were used to determine the reduction in stiffness due to thermal effects. A full-scale finite element model of the bridge superstructure was created, and calibrated based on the fire model and load test results. It was observed through model calibration that the modulus of elasticity in the fire-damaged section of the bridge was reduced by more than 50 percent. This research provided an in-situ performance review of bridge FRP strengthening and effect of fire damage, both critical for the nation’s aging infrastructure.