Performances at high temperature of RC bridge decks strengthened with EBR-FRP

Fiber reinforced polymer (FRP) can be successfully used to externally strengthen reinforced concrete (RC) bridges where fire is not a primary concern. Nevertheless, common maintenance activity on a bridge deck, such as the laying of bituminous paving, can easily lead the FRP to temperatures higher than the glass transition temperature, Tg. Exceeding Tg does not necessarily imply a drastic reduction in strength and stiffness of the reinforcement. Nevertheless, the softening of the resin implies a drastic reduction in its adhesion properties. Therefore, the efficiency of the strengthening system for existing structures, which mainly depends on the effectiveness of the bond between FRP and concrete, is significantly affected by temperature. The relationships suggested by Italian and American codes in order to evaluate the limit strain for FRP debonding at normal temperature are modified to take into account the effect of high temperature. Then, performances at high temperature of RC bridge decks strengthened with externally bonded FRP plates (EBR) are investigated by considering thermal fields in the structural members which are different from the normal ones. Both fire and the laying of bituminous paving on the decks are considered. In addition, the thicknesses of the slabs and the protective layer are varied to assess their influence on the thermal field in the slabs. The results are discussed with reference to both ultimate and serviceability limit states.