Characterizations of RC beams strengthened with carbon fiber sheets

An experimental and analytical investigation of reinforced concrete (RC) beams bonded with fiber reinforced polymer (FRP) has been presented in this dissertation. Previous studies have stated that by bonding FRP to the tension face of an RC beam, both static and fatigue flexural strengths as well as the stiffness can be increased compared to the RC beam without FRP. Organic epoxy has been widely used as the adhesive which bonds the FRP to an RC beam. In recent years, effort has been given to seek a substitute for organic epoxy because of its lack of fire resistance, difficulty in cleaning and toxicity. Few researchers have attempted to use an inorganic epoxy to replace the organic. The inorganic epoxy has some major advantages over the organic resin: (i) resistance to fire, (ii) resistance to UV radiation, (iii) easy handling and no odor or toxin during construction or curing. The reinforcing effect of the inorganic epoxy-fiber system was compared with that of the organic epoxy-fiber system. It was found that beams bonded with inorganic epoxy have comparable static strength, deflection and stiffness to those bonded with organic epoxy. The beams bonded with inorganic epoxy have higher fatigue strength than those bonded with organic epoxy. Under both static and fatigue loadings, the failure of test beams bonded with inorganic epoxy featured the FRP rupture at the maximum moment section while the beams bonded with organic epoxy all failed by FRP delamination.; This dissertation focuses on the characterization of RC beams strengthened with carbon fiber sheets using the inorganic epoxy. Eight RC beams were reinforced with carbon fiber sheets using inorganic epoxy and tested under static flexural loading. Flexural responses have been obtained. An analytical model was developed to predict the moment-deflection relationship. To further investigate the bond problem between FRP and concrete, an FRP-to-concrete bond test has been performed on twelve specimens. A complete beam strength model, applicable to all flexural failure modes, was presented for both inorganic and organic epoxy systems. Based on the complete beam strength model, a general fatigue strength-life prediction method for FRP strengthened RC beam was proposed based on a fatigue test. For a design purpose, a large database of 115 beams was collected and some strength models were verified using the database. A new strength design model was suggested to the Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures by American Concrete Institute Committee 440 (ACI 440).