A Proposal of Guidelines for Bending Resistance of Frp Rc Members in Fire Situation

Several building codes are available for the design of concrete structures reinforced with FRP; nevertheless knowledge on their structural behavior in case of fire is lack and no reliable design method is available. The experimental data available in the literature about the behavior of fiber-reinforced composite materials as well as of concrete slabs reinforced with FRP bars or grids at high temperatures have been carefully examined, determining deterioration curves of bars mechanical properties as a function of the temperature. On the other hand, a calculation incremental-iterative procedure, developed by the authors on the FE solution of the thermal problem and on the assessment of the moment-curvature law of the cross-section at high temperatures, allows the bearing capacity of the FRP reinforced concrete slabs under fire conditions to be assessed. The procedure has been validated on experimental results of fire tests on simply-supported concrete slabs reinforced with FRP bars carried out by the authors. The incremental-iterative procedure allowed the calibration of a simplified analytical method inspired to the well-known “isotherm 500°C method”, also suggested by the EN1992-1-2 for concrete members reinforced with steel bars. A proposal of simplified design method for bending resistance of FRP reinforced concrete members in fire situation is finally suggested.