Experiment and Analysis of CFRP Strengthened Fire-damaged Reinforced Concrete Continuous T-Beams

Experiments of four reinforced concrete (RC) two-span T-beams were introduced. During the experiment, one T-beam was normal temperature control T-beam, and the other three T-beams were heated 75 minutes under ISO-834 standard fire (ISO 834, 1975). Among these three T-beams, One T-beam was unstrengthened control T-beam, and the other two T-beams were strengthened with carbon fiber reinforced polymer (CFRP) sheets. The same test setup was used to loading tests of four T-beams. The results showed that the midspan yield load, ultimate load, stiffness and ductility of the fire-damaged continuous T-beams decreased comparing with these of the normal temperature control T-beam, while ductility and stiffness dropped more sharply. External strengthening with CFRP sheets was found to increase the load capacity and stiffness of T-beams, but the ductility of Tbeams dropped. The way of strengthening using CFRP influenced the moment redistribution of the fire-damaged continuous Tbeams. Tensile rupture of the CFRP sheets was the only failure mode for the strengthened T-beams. The way of moment redistribution of T-beam changed greatly because of the influence of fire. Different from the normal temperature T-beam, the fire-damaged continuous T-beams had obvious moment redistribution at the beginning of the loading because of the variable stiffness along the length of the T-beams. The relationship between stiffness ratio and moment ratio of the continuous beams was deduced as well.