Bridges, Tunnels and other Transportation Structures
Full Session with Abstracts
It is customary for bridge owners to conduct post-fire evaluation of bridges with the objectives of assessing the extent of the damage, determining the bridge safety and developing repair/replacement strategy. Various current evaluation methods assess only the condition of the fire-exposed surface. However, the post-fire serviceability of a bridge predominantly depends on the strength of the core concrete and reinforcements, which in turn depend on the maximum temperature distribution within the member during a fire event. The current study proposed a heat transfer modeling scheme that aids in determining the in-fire internal temperature distribution of prestressed concrete bridge girders based on the results of post-fire evaluation. The scheme requires defining geometry, boundary condition, temperature dependent material properties, analysis method and contact information. Defining the temperature boundary condition involves: (1) dividing the fire affected girder into sections based on the visually observed damage severity; (2) finding the compressive strength of each section using Schmidt Hammer; (3) calculating the fraction of compressive strength lost compared to an undamaged girder; (4) finding the maximum temperature experienced by each section from the relationship between compressive strength reduction and temperature; and (5) defining temperature versus time curve. The proposed method was validated by modeling a carbon fiber reinforced polymer (CFRP) strengthened and thermally insulated prestressed concrete bridge girder subjected to hydrocarbon fire. It was found that the numerically predicted temperature distribution within the girder agreed well with the experimental results. The method can be used in the investigation of similar bridge fire incidents and to make an informed decision.