Thermal protection of reinforced concrete columns strengthened by GFRP laminates (experimental and theoretical study)

Fiber reinforced polymer (FRP) has been used over the last decade in the form of laminates for strengthening reinforced concrete elements. Non-corrosive characteristics, high strength and good fatigue properties of FRP significantly increase the service life of structures. However, FRP have a negligible resistance to fire. This is mainly due to the fact that the epoxy adhesive used in the application of FRP is badly deteriorated by high degree of temperature. The current paper studies fire protection of glass fiber reinforced polymer (GFRP) laminates used in strengthening reinforced concrete columns. The experimental program of this study included testing of seven reinforced concrete circular columns. Two columns were tested as control columns. Five columns were exposed to high degree of temperature, while being loaded, to simulate the actual situation in structures. Two different systems for protecting GFRP laminates against fire were used with varying thickness. Specimens were exposed to high degree of temperature by different durations and then reloaded to measure the residual strength. The behavior and failure modes of the strengthened concrete columns exposed to high degree of temperature are presented. Recommendations for application of protective coating to FRP systems against high degree of temperature are given. Theoretical analysis was also carried out to predict the load capacity of the reinforced concrete columns strengthened by GFRP laminates. Evaluation of the analytical work was introduced and compared to the results of the experimental work.