Page 159 - Riem-Vol6_nº3

504 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 3
Numerical approach of the bond stress behavior of steel bars embedded in self-compacting concrete
and in ordinary concrete using beam models
performed using the specimen geometry shown in Figure 1. The
specimens consisted of a steel bar with 10 and 16 mm of nominal
diameter, anchored in 100 and 160 mm embedded length in the
concrete beam, respectively.
The roughness (including the steel bar ribs) of the steel bar was
not considered and a plain contact surface was adopted in the
numerical study. This assumption was made based on previous
researches that shown the influence of the steel bar ribs were not
significant, due the use of the FKN (normal contact stiffness factor)
and FKT (tangent contact stiffness factor) parameters, according
to the adopted bond model [15-16]. The finite elements used on
the mesh were: for concrete elements, Solid65; for steel elements,
Solid45; for contact surface, Conta174 and Targe170 [20]. Figure
7 shows the constraints for the numerical model.
The load was applied according to the maximum displacement
measured on the test at a constant rate. The mesh was made to
allow the same point of application of the load as was applied on
the test. Table 4 shows the tests results and the values used for
the numerical approach (FKN, FKT and D).
Figure 8 and Figure 9 shows the numerical behavior compared
with the test results.
Table 5 shows the comparison between the numerical and experi-
mental results.
According to Table 5, there was good approach of the numerical
and experimental results. The slip of the numerical model was less
accurate than the displacement prevision for both steel bar mod-
els. The beam model with 10 mm steel bar was better represented
by the numerical model than the model with 16 mm steel bar. This
could be caused by the adopted mesh, which could reduce the ac-
curacy of the numerical approach.
Figure 6 – Numerical mesh adopted
Beam model with 10 mm steel bar. Concrete elements and full model Beam model with 16 mm steel bar. Concrete elements and full model A B
Figure 7 – Considerations for the
numerical model
Beam
Steel
Hinge

bar
Table 3 – Specimens division for tests
Model Concrete type Bar diameter
30 MPa
60 MPa
Concrete compressive strength
B-SCC-C30-B10
B-SCC-C30-B16
B-OC-C30-B10
B-OC-C30-B16
B-SCC-C60-B10
B-SCC-C60-B16
B-OC-C60-B10
B-OC-C60-B16
SCC
SCC
OC
OC
SCC
SCC
OC
OC
10 mm
16 mm
10 mm
16 mm
10 mm
16 mm
10 mm
16 mm