Fire endurance tests of CFRP-strengthened RC beams with different insulation schemes

The fire performance of externally bonded (EB) carbon fiber-reinforced polymer (CFRP)-strengthened reinforced concrete (RC) beams is an important issue in practical strengthening design. The cable mechanism of CFRP sheets in a fire can improve the fire endurance of the strengthened beams. This paper presents a feasible method to activate the cable mechanism of EB CFRP sheets in the strengthened beams by using appropriate insulation schemes and a mechanical anchorage system. Seven beams were constructed: three were tested at room temperature, while the remaining four were subjected to the ISO 834 standard fire. The experimental results showed that the three insulation schemes could provide reasonably good protection for the specimens, and thus all of them achieved a fire endurance of 2.5 h. The combined use of fire insulation and a mechanical anchorage system could reduce the deflection responses, mainly due to the active cable mechanism of the EB CFRP sheets during fire exposure. A finite element (FE) model was then proposed to predict the thermal and structural responses of insulated CFRP-strengthened RC beams. The FE parametric results further indicated that different insulation schemes with various thicknesses and thermal conductivities had significant effects on the fire performance of the strengthened beams.