Design Proposal for Concrete Cover Separation in Beams Strengthened by Externally Bonded Tension Reinforcement
Existing experimental observations have shown that the application of externally bonded reinforcement (steel plate, FRP laminate, overlay, etc.) to strengthen RC structures can lead to brittle failures involving debonding of the external reinforcement before the design load is reached with classical failure modes. The design approach to determine the strengthening material and its area should avoid these premature failures. In this study, an analytical model developed for the overlay strengthening by the authors is firstly proved to be applicable for the steel plate or FRP laminate strengthening by comparing the analytical and experimental failure load as well as the failure mode of the strengthened beams reported in the literature. Then the main parameters involved in the process of concrete cover separation are identified and a simple criterion is proposed for prediction of premature failure.
Abstract Methods of estimating the concentration of effective network chains from the stress—strain behaviour of elastomers both dry and swollen in solvents are discussed. It is pointed out that while measurements in uniaxial extension are more difficult to carry out experimentally than measurements in uniaxial compression, they are preferred because they can provide more information about the behaviour of the elastomer. An equation is presented for relating the stress—strain behaviour of swollen composites containing inert fillers to the behaviour of a gum having the same degree of crosslinking; experimental data on SBR—glass bead composites are presented which indicate that the equation is applicable.