Fatigue and post-fatigue behavior of PBO FRCM-concrete joints

Fiber-reinforced cementitious matrix (FRCM) composites may represent a valid alternative to the use of traditional techniques for strengthening and retrofitting existing reinforced concrete (RC) and masonry structures. Although FRCM composites appear to be an effective strengthening technique for RC structures, limited work is available in the literature. In this paper the behavior of FRCM-concrete joints subjected to fatigue and post-fatigue quasi-static monotonic loading is presented and discussed. The single-lap direct-shear test set-up was adopted in this study. The fatigue loading protocol was designed to investigate the effects of different frequencies and different load ranges on: (a) the interfacial slip; (b) the dissipated energy during cycles; (c) the stiffness degradation of the interface; and (d) the post-fatigue quasi-static monotonic behavior. In general, it was observed that different combination of amplitude and mean value of the load range implies different damage measured in terms of slip, energy dissipation, and stiffness degradation. A fracture mechanics approach was proposed to describe the intermediate range of the fatigue crack growth for different frequencies