Behavior of FRP Reinforced Concrete Slabs in Case of Fire: Theoretical Models and Experimental Tests

Several technical codes allow concrete structures reinforced with FRP to be designed, but few calculation models taking account of fire condition are available. Assuming that the anchoring of the reinforcement is ensured in cooler zones of the structure, a calculation procedure developed by authors allows the flexural capacity of the one-way FRP reinforced concrete slabs under fire conditions to be assessed. The procedure was used for the design in the fire situation of six concrete slabs reinforced with Glass Fiber Reinforced Polymer (GFRP) bars. Such slabs were tested in case of fire by exposing them to heat in a furnace according to 150834 standard time temperature curve: four slabs have been tested under typical design loads in fire situation and two unloaded slabs have been tested after the cooling phase in order to evaluate their residual resistance. The experimental results confirmed that the effects of the high temperatures on both the deterioration of the material mechanical properties and the decrease of bond between FRP reinforcement and concrete are key aspects of the structural behavior of concrete members reinforced with FRP bars. Nevertheless the anchoring length at the end of the members not directly exposed to fire could ensure a fire resistance time higher than 180 minutes.