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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 1
M. K. EL DEBS | E.K. BELLUCIO
to its imperfections. The slope of the straight line represents
the stiffness of the pad (Figure 5).
b) Cyclic Loading
The cyclic loading test is used to determine the evolution
of stiffness when exposed to repeated loading. The basic
scheme of the cyclic test was also used for the monotonic test,
and the pads used in this test have the same dimensions of
the ones used in previous tests (150mm x 150mm base and
thickness of 12mm). The difference is that the loading was re-
peated cyclically and the load values used were similar to the
ones which promote contact pressure of the same magnitude
found in practical situations of use of the bearing pads.
The stress used for this test were the same adopted by Siquei-
ra [6] of 2.5MPa, 5.0MPa, 10.0MPa and 20.0 MPa. By adopt-
ing these values stress, loads in the respective phases of the
tests were approximately 55kN, 112kN, 225kN and 450kN. For
each value of stress, cycles of 50 repetitions for each loading
were performed, corresponding to 0.02mm/s. The loads were
applied to the limits and led to a value close to zero.
Stiffness was analyzed utilizing the load evolution and the ac-
cumulated deformation of cycles. Stiffness is calculated in the
typical manner of the monotonic loading tests. The accumu-
lated deformation is the consolidation of the material, there-
fore, the displacement suffered by the pad during each cycle.
The accumulated deformation is calculated via the difference
between the initial and final value of the displacement cycle
(Figure 6).
4. Results and Discussion
4.1 Mortar characterization tests
Six specimens were tested in three different moldings (two samples per
molding). The average of the results is presented in Figure 7 and Table 1.
Through the analysis of the results it is indicated that adding materials
decreases the resistance of the mortar, but it would still be compatible
with use. The samples of modifiedmixtures did not present brittle fracture
due to the presence of fibers (Figure 8).
Figure 10 – Average results of
concentrated load
Figure11 – (a) Samples test; (b) details of reference sample; (c) details of PP12 sample
A
B
C
Figure 12 – Results of bending tests
of the PP12 mixture