Crack induced interfacial debonding in damaged RC slabs strengthened with FRP

Adhesively bonded FRP patches can be used to strengthen damaged reinforced concrete slabs, which typically exhibit a two-dimensional cracking pattern. The combination of a layered configuration and a cracked substrate designates interfacial debonding as a principal failure mechanism. The present work aims to shed light on the fundamental questions regarding the behavior of this cracked and strengthened layered form, using a high-order multi-layered plate theory and a corresponding finite element formulation, and with emphasis on the modeling of two dimensional plate-type cracks and their impact on the structural response. The analytical-computational platform addresses the manifold challenges involved in modeling the crack induced discontinuities and the two-dimensional evolution of interfacial debonding. The study looks into the behavior of a shear cracked beam and a diagonally cracked and FRP patched square slab. It reveals the unstable, two-dimensional, and not-self-similar nature of crack-induced debonding in two-say slabs. The debonding mechanism is characterized through irregular equilibrium paths and through the interfacial traction profiles that govern its evolution and stability features. The essential differences between the known debonding mechanisms observed in cracked beams and the case at hand are noted and discussed, setting the latter as a new and separate category.