FRCM strengthening systems efficiency on the shear behavior of pre-damaged masonry panels: an experimental study

Existing masonry constructions are highly vulnerable to seismic actions, as demonstrated by the severe earthquakes which stroke the Italian territory in recent years, causing great damages, especially in old masonry buildings. Therefore, restoring damaged buildings, with the aim to recover or improve their structural capacity, is a key aspect in the post-seismic interventions. Fiber reinforced composite materials could be effectively used to this purpose. One aspect which is worth to investigate is the application of these reinforcement typologies on damaged structural elements. Even though many experimental campaigns are available concerning the mechanical improvement given by composite materials applied on undamaged structural elements, only few can be found considering strengthening of already damaged masonry walls. The objective of the work here presented is to evaluate the shear response of damaged masonry panels strengthened using fiber reinforced cementitious matrix (FRCM). Two unreinforced brick masonry walls were subjected to diagonal compression tests, producing an extended state of damage. Afterwards, the same walls were strengthened with FRCM and diagonal compression tests were again performed. Comparisons were done between the results of the unreinforced samples and the pre-damaged strengthened ones, in terms of shear strength and post-peak behavior. The FRCM retrofitting system was also used to strengthen an undamaged masonry panel, which was tested in order to analyze similarities and differences with respect to results obtained for pre-damaged samples. The experimental campaign allowed to study the sole contribution of the reinforcement to the shear capacity of the wall panels. Results showed that the presence of FRCM reinforcements on damaged masonry panels influenced the shear behavior of the samples, which experienced a more ductile failure.