Page 156 - Riem-Vol6_nº3

501 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 3
F.M. ALMEIDA FILHO | M. K. EL DEBS | A.L.H.C. EL DEBS
of reinforced concrete structures. The evaluation of the bond
strength of reinforcing bars in structural concrete elements is
important to evaluate the feasibility of placement self-compact-
ing concrete. There is some experimental data about the bond
behavior comparing self-compacting concrete and ordinary
concrete using beam tests, but there is few data related to
numerical simulations about the bond phenomena. The impor-
tance of this research lies on these two aspects, where it aims
to contribute.
2. Summary of the experimental program
The experimental program was part of a wider research on the
bond behavior on self-compacting concrete. The beam geometry
was based in the model established by [12]. Figure 1 shows the
geometry of the adopted beam.
The position and the inclination of the bars during the casting had
a significant influence on the bond resistance and the specimens
cast in the vertical direction presented larger bond resistance than
the models cast horizontally. The monotonic displacement ap-
plied varied with the bar diameter; so, for 10 mm steel bar, the
displacement rate was 0.01 mm/s and for the 16 mm steel bar,
the displacement rate was 0.016 mm/s, until failure. The deforma-
tion rates were calculated dividing the steel bar diameter by 1000
achieving similar results as Rilem recommendations [7].
Figure 2 shows the test set-up for the beam specimens. The data
from these LVDT were used to determine the slip of the steel bar.
Electrical resistance strain gauges were placed in five points of the
placed close to the concrete prism surface, the concrete splitting
failure occurs. On the other hand, if no reinforcement is added to
the concrete prism, the bond strength depends, almost totally, of
the concrete compressive strength.
According to the current technical literature, the beam test is more
reliable to investigate bond behavior, since it reflects the behavior
under pure flexure and considers the effects of tension cracks.
Few researches were performed using beam models with self-
compacting concrete, being this absence of data a motivation
for this research. According to the literature, SCC appears to
improve the bond strength, due to its filling ability to involve the
reinforcement. This improvement was not significant, but the ex-
perimental data proved the use of self-compacting concrete pos-
sess, at least, the same behavior of similar models made with
ordinary concrete [7, 11].
1.1 Justification
In this paper, the behavior of beams specimens was studied
through experimental tests and numerical analysis using the finite
elements method. The main objective was evaluating the load
vs. displacement and load vs. slip behavior and the bond stress,
regarding the influence of the numerical parameters involved in
the used software. The secondary objective was to compare, by
numerical models, the bond behavior of self-compacting concrete
(SCC) with ordinary concrete (OC), and show the bond stress dis-
tribution on the contact surface.
This research has special significance in construction practice
Figure 2 – Beam test set-up
LVDT LVDT
Steel hinge
Spreader beam
Instron's plate support
Load cell
Instron's hinge
Instron's piston
Support beam
Piston support
Reaction slab
Load
direction
Beam specimen