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1. Introduction
The red ceramic industry is responsible for creating a number of jobs
in Brazil. For instance, in the state of Santa Catarina, there are 742
pottery facilities with a production of approximately 100 million units
per month that are responsible for 11,000 direct jobs and 30,000
indirect jobs. Therefore, this industry is socioeconomically very im-
portant [1]. The pottery sector has approximately the same profile in
almost all Brazilian states, showing both a high production potential
but also the small-scale technological and investment capacity for
creating new products. The red ceramic companies produce various
products including tiles, bricks, and both structural and non-struc-
tural blocks. The main masonry product used for partitioning space
in construction are non-structural blocks containing horizontally ori-
ented circular or rectangular hollows. A Brazilian standard defines
the minimum compressive strength of non-structural blocks. There
are different shapes and thicknesses of structural blocks that will
be further discussed below with regard to their efficiency at stress
distribution in masonry walls under compression.
The increasing use of ceramic block masonry structures as con-
struction systems in the Brazilian building market has been a factor
in generating research projects focusing on development of mason-
ry products that maintain a high efficiency capacity when subjected
to external loads. The main goal of this work is experimentally ana-
lysing and assessing the influence of ceramic block geometry on the
mechanical performance of structural walls under compression on a
small-scale, allowing such blocks to potentially become an important
component for the Brazilian ceramic industry.
2. Use of small physical models
in structural masonry
One of the greatest challenges in civil engineering is to develop
reliable models for representing the behaviour of structures on a
full scale, thereby reducing the costs and the difficulties associated
with “experimenting” with a full scale. The physical modelling of
structures requires understanding of the similarity of the conditions
of the models to truly to reproduce the behaviour of full-scale struc-
tures with regarding to predicting the ultimate stress, failure modes
and stiffness. Physical models therefore should reproduce the full-
scale loading, geometry and material properties [2].
One of the first authors to historically depict the use of physical
models in structural masonry was ABBOUD et al. [2]. ABBOUD
et al. reported that VOGT [3] carried out experimental studies on
bricks masonry models at 1:4 and 1:10 scales, but failed to obtain
consistent data regarding the behaviour of the material. ABBPID
also cites that, in the 1960s, studies were performed at Melbourne
University with limited success because of difficulties in manufac-
turing bricks and constructing walls. ABBOUD also mentions that
MOHR [4] achieved success in the execution of walls by using
commercial units and prefabrication techniques at a 1:6 scale.
The studies carried out by ABBOUD et al. [2] with concrete blocks
units showed that there was reliability to be gained from using
small models for predicting the complex behaviour of structural
masonry. ABBOUD obtained excellent correlation between model
results when compared to prototypes, but the standard deviation
was smaller in prototypes. This result was obtained by reduction of
the effect of stress volume.
In Brazil, CAMACHO [5] was the first to perform studies on
the compressive behaviour of block masonry. The author stat-
ed that masonry is the oldest and most classical construction
method used by man, while the implementation of the small
model technique for studying structural behaviour is very recent.
CAMACHO [5] affirms that studies were carried out at the Uni-
versity of Bath and Karlsruhe University in Germany, regarding
the behaviour of small masonry model walls made with ceramic
bricks at scales of 1:2 and 1:4. CAMACHO states that those
studies allowed the researchers to determine the strength cor-
relations and deformations and therefore verify the parameters
that would be affected by a scaling factor. Based on small-scale
tests, it was concluded that masonry models can reproduce the
failure mode and the ultimate strength when similar materials
between the models and the prototypes are employed. How-
ever, the value of the relation between the elasticity modulus
based on compression strength was reduced with the decreas-
ing of the scale, as shown in Figure 01.
CAMACHO [5] carried out experimental studies with hollow
clay masonry blocks on full-scale model sand small scales of
1:3 and 1:5. The author performed compressive strength tests
of prisms that were two, three and four blocks high as well
as small walls. The compressive strength results for blocks,
prisms (two, three and four blocks height) and small walls and
the stress/strain results for blocks are shown in Figures 02
and 03, respectively. The author concluded in general that
axial compression strengths between the small scale and the
full-scale prototypes were similar but that for prisms and small
walls, the small scale models presented compressive strength
values 1.5 times higher for prisms and 1.3 times higher for
small walls compared with the prototype. The strain at failure
for the small scale and the prototypes were of the same order
of magnitude, but the small-scale prisms had 2.4 times the
prototype strain, while the small-scale small walls had strain
values that were 4.5 times the prototype. In addition, the rela-
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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 5
E. RIZZATTI | H. R. ROMAN
|
G. MOHAMAD | E.Y. NAKANISHI
Figure � � �elationship �et�een modulus
of deformation/compression strength
for different scales (CAMACHO [5])