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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 �� � �etermination of elasticit�
modulus of the wall under compression
stress level of 30% of the compression strength. For measure-
ments of the initial stress and strain, different characteristics of
elasticity modulus of the walls depending of the block geometry
were observed, especially for block types B and C. This differ-
ence between blocks B and C was a factor of 1.8. This difference
is not thought to be due to the geometric shape of the block but is
rather due to the level of confining stress in the mortar caused by
friction between the block surface and the bedding mortar joint.
For this level of stress, the mortar joint is the main cause for the
deformation of walls. The value of
“Ritter constant”
was lower
than those specified in Brazilian and international standards. The
Brazilian Standard NBR 15812-1 [20], shows a Ritter constant of
600 while ES 6 [21] recommends a value of 1000. This fact may
be related to the degree of compaction of the mortar joint dur-
ing the bedding of the units, as suggested by ABBOUD [2] and
CAMACHO [5].
5. Conclusions
Based on the results, the following can be concluded:
n
Blocks with a double central web presented the best perfor-
mance in wall compression compared to the others. This con-
clusion is confirmed by the efficiency factor of the set (block
and mortar);
n
Compression tests on stack-bonded prisms with a half-block
in the intermediate course were not adequate for checking the
influence of the geometry. For the cases studied, the efficiency
factor ranged randomly from 0.35 to 0.47 without demonstra-
tion of similar behaviours for the same shapes of hollows;
n
There were no significant differences in the compressive
strength of walls caused by increasing mortar strength, with
it likely the case that the scale reduction decreased the influ-
ence on the strength most likely the reduction on the scale de-
creased this influence;
n
The strength and the corresponding efficiency factors showed
that strength potential among prisms and walls decreased;
n
Three-block prisms with an intermediate layer consisting of two
half-blocks did not produce lower efficiency factors compared
to three-whole-block prisms;
n
D-shaped blocks provided a more uniform distribution of trac-
tion tension than the other geometry shapes due to the coinci-
dence of the webs in transversal walls of the block;
n
It was found by the results between the deformation modulus
by compression strength (
“constant of ritter”
) that the values
were significantly lower on the small scale. This finding was
demonstrated by the mortar bedding degree at the moment of
unit bedding;
n
The failure mode of prisms and walls on a small scale were
similar to the ones found in the literature cited in this work. It
can therefore be stated that the study of small models is able
to reproduce trials at a scale that is an efficient, practical alter-
native to full-size trials. The failure mode of prisms and walls
was the crushing of bedding mortar joints followed by contact
cracking of blocks and bending mortar.
6. References
[01] BRDE. Banco regional de desenvolvimento do extremo
sul. Cerâmica vermelha: informe setorial. Florianópolis,
SC, Dezembro, 1994, 14 P.
[02] ABBOUD, B. E.; HAMID, A.A.; HARRIS, H.G.
Small-Scale modeling of concrete block masonry
structures. ACI Structural Journal, Detroit, v.87, n.2,
p.145-155, mar/apr. 1990.
[03] VOGT, H. Consideration and investigation on the
basic principle of model tests in brickwork and
masonry structures. Garston: Building Research
Station, 1956. 30p.
[04] MOHR, G. A. Slender load bearing brickwork walls with
returns. Parkville: University of Melbourne/Civil
Engineering Department, 1970. Thesis (MESc)-
University of Melbourne, 1970.
[05] CAMACHO, J.S. Contribuição ao estudo de modelos
físicos reduzidos de alvenaria estrutural cerâmica.
Tese de doutorado, Universidade de São Paulo, 1995.
[06] NETO, J. A. do N. Estudo de painéis com abertura
constituídos por alvenaria estrutural de blocos. Tese
de doutorado, Escola de Engenharia de São Carlos,
Universidade de São Paulo, 2003.
[07] GOMES, N. S. A resistência das paredes de alvenaria.
Dissertação de mestrado, Escola politécnica da
universidade de São Paulo, 1974.
[08] MENDES, R. J. K. Resistência à compressão de
alvenarias de blocos cerâmicos estruturais. Dissertação
de mestrado. Programa de pós-graduação em
engenharia civil da Universidade Federal de Santa
Catarina. Florianópolis, SC, 1998, 185 P.