IC Debonding Strength Model Of RC Beams Flexural-strengthened With Externally Bonded FRP

Fiber Reinforced Polymer (FRP) has been widely applied in the strengthening of reinforced concrete structures due to its advantages, such as ligh tweight, high strength and good corrosion resistance, etc. Externally bonding (EB) FRP to the soffit of reinforced concrete (RC) beam (referred to as FRP-plated beam) for flexural strengthening is one of such applications. FRP-plated beam is featured by different types of brittle FRP debonding failures, among which intermediate cracks induced debonding (IC debonding) is a typical debonding failure. IC debonding usually initates at the end of the most cirital flexuaral crack in an FRP-plated beam, and progagtates to one of the plate end; a think-layer of concrere can always be seen attached to the debonded FRP surface, implying that the debonding accutrally occus in the concrete layer adjacent to the FRP-to-concrete interface. To prevent IC debonding failures, different IC debonding strengths model have been proposed/developed by exisiting researchers or suggested by existing FRP guidelines; most of the existing strength models have been based on and/or substantiated against FRP-plated RC beams tested by three-point or four-point bending, implying that these model cannot reflect the effects of load distribution. Against the above background, this MSc thesis proposed a IC debonding strength model capable of considering the interaction between adjacent cracks in FRP-plated beams, aming to remove the above drawback of the existing strength model. A large test database of IC debonding was then established to assess accuracy and rationality of the proposed model; from the assessment results, the advantages of the proposed model over existing models can be demonstrated. The main contents covered in this thesis inlcude:(1) An IC debonding strength capable of considering the interaction between two adjacent cracks was proposed based on the analytical study of Chen et al. (2007); according the implementation process, the proposed model can be further classified as iterative model and simplified model.(2) A large number of test data, including the test data of 305 FRP plated beams failying by IC debonding, were collected from existing literature,based on which a large test database for IC debonding was established.(3) The test database estabilished in step (2) was deployed to assess the performance of three famouse crack spacing models of FRP-plated beams when they were used in the proposed IC debonding model.(4) Aslo using the test database estabilished in step (2), the performance of the proposed IC debonding strength mode as well as a number of other existing strength models, were carefully assessed in terms of a number significant staticits indexes, such as the average value(Avg) of ratios between predicted values and test values, standard deviation (SD), coefficient of varation (Cov) and correlation coefficient. The assess results showed that the proposed IC debonding is overally advantegous than other existing models.