Thermomechanical properties of constituent materials for evaluating fire resistance of FRP-strengthened concrete structures

Numerical models are exceedingly being used for evaluating the fire resistance of structural members, wherein temperature-dependent thermomechanical properties of the materials are an essential input requirement. Substantial amount of comprehensive test data and constitutive relations are available for defining elevated temperature thermomechanical properties of concrete and reinforcing steel; however, only limited information is available on the temperature-dependent properties of fiber-reinforced polymer (FRP) and fire insulation. This chapter reviews the currently available elevated temperature property test data and associated relations for FRP and highlights the variation in them. Additionally, the influence of different high-temperature property relations on the fire resistance predictions of FRP-strengthened concrete structural members is discussed. Furthermore, a numerical case study is presented to illustrate the applicability of the recommended temperature-dependent thermomechanical relations for concrete, steel rebar, and FRP as well the recommended thermal properties of fire insulation on fire resistance prediction of the FRP-strengthened member. Results from the analysis indicate that recommended property relations for concrete, steel rebar, FRP, and fire insulation can evaluate the fire response and fire resistance of the strengthened concrete members with reasonable accuracy. In the end, recommendations are made for appropriate property relations of concrete, steel rebar, FRP and fire insulation in evaluating fire resistance of FRP-strengthened concrete members.