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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 2
R. M. F. CANHA |
G. M. CAMPOS |
M. K. EL DEBS
gion. Table 3 presents the resulting forces in the reinforcement
tmh ,s
A
according to the variation of
r
β
of the rear transverse
wall.
An analysis of Table 3 indicates that the compression struts incli-
nations on the tension side of the socket (rear wall) are smaller
than those of the compression struts on the compression side
(front wall). Hence, for this wall, angles of 35
o
and 45
o
were ad-
opted in this study. The rear transverse wall was instrumented
only in specimens IR-3 and IR-4. Table 3 shows the data for
these two sockets.
As it can be perceived, for the two specimens under bending-
tension condition, and considering an angle of 45
o
, the obtained
theoretical forces in the internal branch of the reinforcement were
smaller than the observed experimental values, hence this strut
angle is not recommended to consider. If an angle of 35
o
is consid-
ered, the verification of forces for specimen IR-4 is not neglected.
The theoretical force in specimen IR-3 was found to be slightly
smaller that the observed experimental value, but as it can be re-
called, this specimen had a reduced embedded length.
Notwithstanding the few experimental results available, it is recom-
mended that a value of
o
r
35
=b
be adopted, because considering
this situation, the theoretical force is higher than the experimental
value. A strut angle of 30
o
was not considered since the corre-
sponding results for this situation would be very conservative rela-
tive to tension or more still, would not meet safety conditions for the
case of bending-tension.
It is worth emphasizing that in the knowledge of the authors, this
formulation is currently the only model available for analyzing the
rear transverse wall.
2.3.2 Main longitudinal horizontal reinforcement – A
s,lmh
As indicated in Figure 6, the reinforcement
lmh ,s
A
located on
the upper part of the longitudinal walls of the rough socket must
be determined considering the effect of the pressures
topf
H
and
topr
H
acting on the transverse walls of the socket.
The main horizontal reinforcement is made up of two branches:
Table 3 – Theoretical and experimental internal forces in reinforcement A
s,tmh
with varying angles o
β
for the rear transverse wall of rough interface sockets
r
Specimen
Design
model
Angle
b
r
R (kN)
s,tmhe
R (kN)
s,tmhi
Theoretical Experimental
Theoretical Experimental
IR-3
Bending-
tension
45º
159.90
31.20
35º
228.40
44.50
Tension
45º
112.40
112.40
35º
160.50
160.50
IR-4
Bending-
tension
45º
199.60
24.10
35º
285.10
34.50
Tension
45º
131.60
131.60
35º
188.00
188.00
100.30
101.30
46.50
33.80
external and internal branch, and must be distributed in the upper
part of the socket within a height of
l
emb
/3
.
After determining the pressures acting on the transverse walls, it
is recommended to estimate the resulting steel area based on the
pressure on the front and rear walls. An estimate of this reinforce-
ment is carried out following equations 15 and 16, and the adopted
lmh ,s
A
is the highest of the obtained values.
(15)
yd
topf
lmh ,s
f2
H
A
×
=
(16)
yd
topr
lmh ,s
f2
H
A
×
=
2.4 Secondary reinforcements – A
s,sv
and A
s,sh
Figure 6 illustrates the positioning of the secondary vertical rein-
forcement A
s,sv
and the secondary horizontal reinforcement A
s,sh.
These secondary reinforcements are used in socket foundation
to resist secondary stresses and for cracking control of pedestal
walls. It is noteworthy that the secondary horizontal reinforcements
used in the front wall play the important role of absorbing the pres-
sures within two lower thirds of these wall (
2
l
emb
/3
).
For calculation of the secondary reinforcements of socket with
rough interfaces, it is recommended to apply the short corbel the-
ory for the longitudinal walls, respecting the following areas and
spacings indicated in El Debs [14]:
n
For secondary vertical reinforcement:
mv ,s
lsv ,s
tsv ,s
sv,s
A40,0 A A A
×
³ = =
n
For secondary horizontal reinforcement:
mv ,s
lsh ,s
tsh ,s
sh,s
A25,0
A A A
×
³ = =