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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 1
A. D. de Figueiredo | A. de la Fuente | A. Aguado | C. Molins | P. J. Chama Neto
a situation which took place when load
F
reached average values
of 126 kN, 114 kN and 138 kN for the pipes with 10 kg/m
3
, 20 kg/
m
3
and 40 kg/m
3
, respectively. So, the load
F
cr
can be deduced
from the load-displacement curve at the point where the first slope
change takes place. On the other hand, if the measurement is per-
formed as in the 1
st
Series, this procedure would lead to values of
F
cr
on the side of insecurity, requiring a visual inspection in order to
detect
F
cr
., which could indicate if the control load fits the standard
requirements. Since the load displacement curves obtained to the
2
nd
Series of tests showed that linear region finishing when the load
was about 90 kN. Thus, these pipes would be probably approved
because is possible to associate this level of loading to the
F
cr
..
The Brazilian standard requirements [2] for FRCP are a little broad-
er than the European [4]. This is because, besides the load control
(
F
c
) of 90 kN and ultimate load (
F
u
) of 135 kN, common to both, the
Brazilian standard requires a minimum post-peak load (
F
min,pos
) of
94, 5 kN. This fact increases the importance of the post-peak resid-
ual strength of the pipes. As the tests performed for this study have
not the cycle of loading, this parameter could not be determinate
in order to evaluate if the pipes comply with the requirements. Nev-
ertheless, a displacement level was fixed in order to determining a
residual strength in the post-peak region to assess the influence of
the fiber in this specific behavior of the pipe. The results presented
in Table [3] and also in Figures [15] and [16] were used for the
evaluation of this condition. As tests were performed continuously
without re-loading cycle, it was adopted a reference displacement
a little beyond post-peak instability limit for each series. Conse-
quently, the displacements of 1.2 mm and 3 mm were adopted
for determining the post-cracking load for the first and 2
nd
Series,
respectively. The different level of displacement was chosen due
to the disparity in geometric rigidity of pipes observed when the
displacement was measured only at the spigot or at the spigot and
socket. That condition provides different level of displacement for
the same level of cracking and post-peak residual strength.
In Figures [18] and [19] are presented the correlations between the
fiber content and ultimate load (
F
u
) and the post-cracking load at
Table 3 – Maximum load and maximum post-peak load obtained in the two series of tests
Series
C
f
3
(kg/m )
F (kN)
u
F y F (kN)
1.2mm 3mm
Individual values Average
Individual
values
Average
st
1
10
149 120 n/a
135
107
94
n/a
101
20
140 124 n/a
132
118
102
n/a
110
40
156 163 149
156
-
-
-
-
nd
2
10
127 132 138
132
97
88
98
94
20
151 145 129
142
121
120
108
116
40
152 140 193
162
-
-
-
-
Figure 18 – Correlations between ultimate
load and fiber content for both series of tests
Figure 19 – Correlations between fiber
content and the post-peak load at the
displacements of 1.2 mm and 3 mm for
nd
the first and 2 Series of tests respectively