Fire resistance of concrete slabs reinforced with FRP bars. Part I: experimental investigations on the mechanical behavior

Several building codes are now available for the design of concrete structures reinforced with FRP even if no calculation model taking account of fire conditions has been suggested. Only the Canadian code (CAN/CSA 806-02) provides a design procedure in fire situations based on critical temperature. Furthermore, the literature provides some significant experimental results of failure tests performed on FRP–reinforced concrete members working in flexure that were exposed to conventional fire conditions. Tests recently performed by the authors allowed the behavior of six concrete slabs reinforced with GFRP bars exposed to fire action to be evaluated: four slabs were tested under typical design loads in fire situations (40% and 60% of design bending moment resistance at normal temperature) and two unloaded slabs were tested after the cooling phase in order to evaluate their residual resistance. In the present paper the experimental programme is extensively reported, giving detailed information on tests to highlight the practical significance of the experimental research. The results of investigations are discussed with particular reference to the structural behavior of concrete members once the glass transition temperature in the bars is attained and resin softening reduces adhesion at the FRP-to-concrete interface. Results are shown with the aim of providing suggestions for updating design codes. In a companion paper the pattern of temperatures recorded during the tests by means of thermocouples applied both on the surface of bars and in the concrete are presented in depth and compared with results of numerical simulations.