New Materials for the Rehabilitation of Cultural Heritage - Czech ...

New Materials for the Rehabilitation of Cultural Heritage 22
t
int
ft
, calc �t
m
� 1.
2 � . (11)
f
c,
int
Similarly, the minimum resistance of the GFRP wire of the mesh, for a certain grid dimension
p, may be evaluated with the relationship
R
f
� . 3�f
t,
calc
p
0 �t
, (12)
m
where fc,int is the compressive strength of the coating mortar.
The equivalent shear modulus of the strengthened masonry Gcalc may be assessed with the
relationship
G
calc
� t �
�
� int
��
�G
m �2
�G
int �
�
�,
(13)
� tm
�
where Gm is the shear modulus of unreinforced masonry, Gint is the shear modulus of coating
mortar. The coefficient �may be assumed equal to the coefficient �.
4.2.3 CAM system
Ancient masonry structures are often characterized by irregular or multi-layer masonry walls,
with lack of transverse connections. The need for compacting them to improve their
mechanical characteristics suggests the idea of using a three-dimensional system of tying. The
CAM system [6], Active Ties for Masonries, is based on such idea. Ties are made of stainless
steel thin strips (0.8x20 mm) and are pretensioned, so that a light beneficial precompression
state is applied to masonry. Special connection elements permit to realize a continuous
horizontal and vertical tie system, so that the shear and bending in-plane and out-of-plane
strengths of single panels and entire walls are improved. The main characteristics of the CAM
system are illustrated in Fig. 16, whereas in Fig. 17 two examples of applications are shown.
(a) (b)
Figure 16 –CAM system: (a) arrangement of the tie system, (b) detail of one node of the grid.