One of the main technical strategies for seismic upgrading of ordinary masonry buildings, often
utilized after earthquakes, consist in strengthening walls by means of thin reinforced mortar slabs
applied at one or both sides of the wall and linked to it. This type of technical provision has been
currently employed in Italy and widely utilized after the 1976 Friuli earthquake. In spite of this,
no experimental investigation has been performed until now to asses structural behaviour of the
composite structure masonry wall-reinforced mortar slabs. In this work an experimental
investigation has been carried out on masonry wall panels strengthened with different technical
and executive strategies commonly used for ordinary masonry of private building. To evaluate
shear strength of strengthened masonry walls, four wall test units (panels) with dimensions of
100x100x25cm and subjected to in-plane loads have been experimented. One of the wall panel
was made of ordinary masonry, one was strengthened by a reinforced mortar slab applied only on
one side, one had reinforced mortar slabs on both sides but anti-adherent sheaths between the
masonry panel and the slabs to simulate the case of bad realization of the upgrading, and one had
slabs on both sides and perfectly adherent to it. The study shows the importance of realizing a
good adhesion between the masonry wall and the reinforced mortar slabs. Indeed increase of 26%
in strength of about has been observed in the composite wall panel with perfectly adherent slabs
in comparison to the composite wall panel with anti-adherent sheaths between the wall and the
slabs.
