Performance of FRP-Strengthened Beams Subjected to Elevated Temperatures

The flexural behavior of fiber-reinforced polymer (FRP)–strengthened beams after exposure to elevated temperatures in an electrical furnace was investigated. Twenty-five specimens making up unstrengthened beams and FRP-strengthened beams were fabricated. Glass and basalt FRP systems were used with and without protective systems, which included a cement mortar overlay and two types of commercially available intumescent coatings. Typical temperature-time histories at the surface of FRP laminates, FRP-concrete interface, internal steel bars, and center of beams were monitored by using two specimens. The other specimens were tested to failure under three-point bending after subjecting them to elevated temperatures. Test results indicated a general decrease in the initial stiffness and ultimate strength of the specimens with an increase in the exposed temperature. The protective systems appeared to preserve the structural integrity of glass FRP systems when the elevated temperature was less than approximately 700°C. Basalt FRP-strengthened beams exhibited smaller deterioration in ultimate strength than glass FRP-strengthened beams.