Keywords :
deep beams, FRP, shear, kinematics-based approach
Abstract :
[en] Strengthening of reinforced concrete beams with externally bonded FRP sheets can be effective in increasing the shear carrying capacity. However, while the shear strength of slender beams with FRP sheets has been studied extensively, there remain gaps in modelling the FRP strengthening of deep beams. Deep beams often exhibit wide diagonal shear cracks prior to failure, which needs to be considered in FRP strengthening strategy. To do so in a rational manner, it is necessary to explicitly model the opening of the cracks, as well as the debonding/rupture behavior of the FRP sheets as a function of the crack displacements. To this end, a kinematic-based model is proposed for shear critical deep beams with FRP sheets with different configurations, i.e., fully-wrapped, U-shape, and side sheets. With the aid of bond-slip models for FRP sheets and the crack displacements provided by the kinematic framework, it becomes possible to capture the full shear response of deep beams with FRP sheets, including the post-peak behavior. The proposed modelling approach predicts how the different shear mechanisms of deep beams (i.e., critical loading zone, aggregate interlock, transverse reinforcement, dowel action and FRP sheets) superimpose and contribute to the shear strength. The model is validated with experimental results showing adequate predictions for members with a large variety of properties.
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