The experimental behavior of FRP-strengthened RC beams subjected to design fire exposure

The results from fire resistance experiments on five rectangular reinforced concrete (RC) beams are presented in this paper. Four of these RC beams were tested after being strengthened with carbon fiber reinforced polymer (CFRP), while the remaining one was tested as a control RC beam specimen. The beams were tested by exposing them to fire and service load, computed based on the nominal capacity of an unstrengthened/strengthened beam in accordance with ACI 318/ACI 440.2R provisions. The test variables included type of fire exposure, anchorage zone, insulation type, and restraint conditions. The data from the fire tests is used to evaluate the thermal and structural response, as well as failure patterns in FRP-strengthened RC beams. The test results indicate that the anchorage configuration plays a critical role in limiting the deflections of the strengthened beam after debonding of the FRP occurs at Tg±10°C, where Tg is the glass transition temperature. Also, FRP-strengthened RC beams supplemented with 25 mm thick spray-applied insulation can survive failure under ASTM E119 standard fire or a design fire. Further, the fire-induced axial restraint force significantly increases the fire resistance of FRP-strengthened/unstrengthened RC beams, provided that the location of restraining force is below the geometric centroid of the beam and that the beam's deflection is sufficiently small along the entire span.