or double laps [4,24–26,37] push–pull shear tests. In
order to avoid eccentricity phenomena and to verify the efficiency
of the methodology, a double lap set-up was preferred in this work.
A recent wide experimental campaign on masonry, detailed in [24],
demonstrated that this testing set up is easy, economic and
reliable.
An even distribution of the load between the two laps may be
usually assumed. This could be verified in each test applying two
instruments on the opposite sides of the bricks but with extra
costs. During all the tests great attention was paid to verify the
symmetry and the similar behavior of the two laps during the
loading.
The testing rig for double-lap experiments was made with a
steel frame composed of two transversal beams connected by four
bars (Fig. 21). In order to minimize the effects of possible misalignments
a spherical joint was positioned in the upper part of the rig.
To guarantee even distribution of the load on the composite strips,
the textile was placed around a cylinder with a diameter equal to
the thickness of the brick and the relevant mortar. Two Teflon
sheets were used to avoid friction and facilitate the even distribution
of the load.
Two different geometries of the reinforcements were considered:
glass fiber grids were bonded to two opposite sides of a single
brick [27]. On the contrary carbon, PBO and PBO-G grids were
bonded on a specimen composed of three bricks and two mortar
joints.
Different bond lengths and widths were considered in order to
investigate the effect of these parameters on the debonding
strength and failure modes. Table 11 shows the layout of the
experimental tests.