Fiber-reinforced-polymer (FRP) composite materials have the required stiffness and strength properties for the flexural and shear strengthening of reinforced-concrete (RC) structures. However, evaluation of the total deflections of RC structures strengthened with FRP composite materials up to their collapse is relatively difficult due to the complexity in shear mechanism and responses of these strengthened structures. These complexities are even more pronounced when the considered structures are statically indeterminate, since in these cases, the external and internal forces cannot be determined from direct application of the equilibrium equations. Hence, the current study aims to develop a comprehensive simplified analytical model based on the flexibility (force) method to predict the total deflections of statically determinate and indeterminate FRP strengthened structures, composed of the flexural and shear deformations. Moreover, after concrete cracking initiation stage, the proposed analytical model offers the consideration of degrading effects of flexural cracks on the shear stiffness in addition of the flexural stiffness, which is a challenge in this aspect. Furthermore, in this model the shear deformation, which has different level of contribution for the prediction of total deflection, can be separately predicted. The predictive performance of the proposed analytical model for these types of structures is verified through the comparison with the relevant experimental results and a good predictive performance is evidenced.
Analytical prediction of load-deflection relationships of: a) strengthened continuous slab, b) RC beam strengthened using U-wrapped GFRP sheets