Bond Behavior of Standard and Reinforced Anchorage between CFRP Sheet and Natural Calcareous Stone

In the past two decades, CFRP had been used to strengthen and repair r.c. structures and recently it is also employed to strengthen historical or monumental buildings constituted by masonry structure. However, premature failure due to debonding of the FRP is one of the important issues still to be resolved. Numerous word wide research studies have dealt with the debonding problem in r.c. structures but only a few works were carried out in the masonry structures area. So, the study of the global behaviour of the reinforced masonry element seems to be very useful, both for a congruous design and to verify the strengthening strategy. To this aim, this paper summarizes the debonding phenomena between C-FRP strip and natural calcareous rock brick, employed in our buildings, by means of a testing investigation. Two different kinds of anchorage were designed and employed for the tested samples: standard and reinforced anchorage. The experimental tests carried out on the specimens permits us to compare the effective bond length, with the one obtained by International rules and especially with the Italian CNR-DT200/2004 formulation and to say that the effective bond length dictates by the rules undervalues the experimental data. The data obtained permit us also to know the shear- slip delamination curve useful for the numerical investigation, as well as both the failure mode and the “II mode” fracture energy