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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 3
P. P. NASCIMENTO | R. B. GOMES
|
L. L. J. BORGES
|
D. L. DAVID
of failure load of Column P2. Figure 12 shows the horizontal dis-
placements measured on the tensioned face of all columns (half
height) and since the beginning of the tests till values close to
failure (to prevent failure, the
dial indicators were removed
before clear signs of rupture);
column P2 showed larger dis-
placements than that of the
other columns. This result of
column P2 cannot accurately
indicate the expected capacity;
however, along with columns
P5 and P8, it shows proximity
to the limit. Greater control of
initial eccentricity is suggested
for future tests.
In Table 2 and Figure 11 it is
possible to see that not only the
number of connectors but also
their location influence the fail-
ure load of the models tested.
It appears that, keeping the
number of connectors constant
and changing their position may
produce considerable load in-
crease, as what happened to
the columns P3, P4 and P5.
These were strengthened with a
single pair of connectors which
were progressively moved away
from the centre. Column P3 re-
vealed the lowest failure load of
the three, whereas column P4
showed a 20% increase over
P3 in failure load and column P5
had a 28% increase in relation
to P3. It appears that the more
distant from the center, the greater was the failure load achieved.
Despite the load increase, these three columns showed abrupt fail-
ure due to uncoating of the strengthening concrete, when compared
with the original reference col-
umn P1.
Due to the fact that column
P5 - strengthened with a pair
of connectors placed furthest
from the centre of the column,
as shown in Figure 7 - was the
strongest of the columns re-
inforced with only one pair of
connectors, thus surpassing
the load of monolithic refer-
ence column P2 by 11%, and
that column P6 had problems
during assay by showing low
failure load, we decided to cast
three more columns. Column
P6A had the same character-
istics P6 did. As to columns P7
and P8, we decided to place a
pair of connectors on the fur-
thest positions from the cen-
tre of the column and we also
added another pair to P7 and
two more pairs to P8.
When comparing columns
P6A and P7, which were dif-
ferentiated from each other
by the location of the sec-
ond pair of connectors, we
observed that, unlike what
we had seen on the columns
strengthened with a single
pair of connectors, there is an
increase in failure load (12%)
Figure 9 – Self-compacting concrete (SCC)
Slump flow test
A
L-Box test
B
Funnel test
C
Figure 10 – Column test setup (mm)
Load cell
R 3
Load cell
Jack
Column
Dial gauge
Strong floor
1000
1000
2000
220
780