Basic HTML Version
474
IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 4
Parametric study on the behaviour of bolted composite connections
Based on measurements of displacement and applied force it was
generated the bending moment curve
versus
rotation. Based on
this curve it was possible to determine the stiffness of the con-
nection. The measurement of displacement of the first transducer
(closest to the connection, Figure 7) was used to determine the
connection rotation. From these values it was calculated the arc
tangent of the angle produced with the starting position of the
beam. The arc tangent corresponds approximately to the connec-
tion rotation.
The cyclic loading was applied to the structure by a device de-
veloped specifically for this function. This device allowed the ap-
plication of displacement reversals which generated in the connec-
tion the positive and negative bending moments at the same time.
Another function of this device was to prevent the appearance of
horizontal forces that could damage the hydraulic jack. Details of
this device are shown in Figure 8.
The loading started with four cycles of 60 kN, then the load-
ing was increased in 25%, reaching 76 kN, when four cycles
more were performed (Figure 9). At the fourth cycle there
was a failure of the structure with the detachment of the slab
caused by the rupture of the concrete in the region of the
shear connectors located near the point of force application,
as shown in Figure 10. The intensity of the cycles was defined
based on previous analytical studies conducted according to
requirements code. It should be noted that another loading
stage was provided with intensity equal to 95 kN, however,
by reason of failure occurred in the slab-beam connection it
cannot be achieved.
4. Experimental results
The maximum vertical displacements below the point of force ap-
plication were 55.85 mm for the right side of the model and 54.46
mm for the left side to the force corresponding to 76 kN. The failure
of the model occurred with the rupture of the connection between
beam and slab, performed by shear connectors. Due to this oc-
curred, it was not possible to reach the failure of beam-column
connection, which according to the code [8] would occur when the
hydraulic jack reached approximately 95 kN.
In Figure 11 is shown the force
versus
displacement curves where-
in it is possible to note that there are not symmetric to the posi-
tive and negative bending moment. As a result of the asymmetric
model, due to the presence of the slab, the bending moment
ver-
sus
rotation curves, presented in Figure 12, show that the bottom
part of the connection rotated more than the top, for the both side
of the model.
The stiffness for the last loading cycle of the left side of the
model was 26398.87 kNm/rad for the bottom of the connection
and 33656.42 kNm/rad for the top, respectively for positive and
negative bending moment. For the right side, the difference be-
Figure 9 – Representation of loading cycles
of Model 1
Figure 10 – Failure of the slab-beam connection