On the competition between delamination and shear failure in retrofitted concrete beams and related scale effects

In this paper we deal with the most commonly reported failure modes related to interfacial stress concentrations at the FRP cut-off points, i.e. diagonal (shear) crack growth and FRP delamination. Depending on the mechanical properties of the tested beams, their geometry and size, a prevalence of a given failure mode to the other is very often experimentally observed. To analyze this failure mode competition, a combined analytical/numerical model is proposed for the determination of the critical loads required for the onset of delamination or shear failure. In this way, the experimentally detected failure modes observed in RC and FRC beams are reexamined and interpreted in this new framework.