Geology Reference
In-Depth Information
During the tests the actuator displacements
and the displacements in correspondence of the
horizontal stiffeners of the panels have been mea-
sured through 8 LVDTs with a stroke of 10 mm
and accuracy <0.10% (Figure 15). A 100 kN load
cell measures the load applied at any time. It was
thus possible to determine the force-displacement
plots described in the following section.
details improved after the first preliminary tests.
The same plot obtained for 40 kN panel is re-
ported in Figure 19.
From the various load cycles, it is possible to
confirm that the area of hysteresis, corresponding
to the energy dissipated by the device, starts from
the earliest load cycles, and increases signifi-
cantly with increasing load level. The origin of
this dissipation resides on two dominant factors:
Results of the Characterization Tests
•
Friction between the plates of steel and
aluminum
The devices first tested were the 20 kN type. They
were subject to subsequent load cycles from zero to
a maximum load in both directions. In subsequent
cycles, maximum load was increased up to failure.
Load cycles having maximum loads greater than
20 kN are performed in one direction only.
These preliminary tests were completed when
the welding at the base of the panels began to failure
(Figure 16). The crisis of welding has also led to
a slip out of the plane of the device, as best it can
be seen in Figure 17. For this reason the details
have been improved, shifting the welding of the
steel plates in points farther from the fixed joints
with the base plate, keeping always the dimen-
sions obtained from the optimization procedure.
The structural behavior of the panels is repre-
sented by the applied load against displacement,
as reported in Figure 18 for 20 kN panel, with the
•
Yielding of materials, presumably
aluminum
Figure 20 shows the cyclical characteristics
curves considering the peaks of the different hys-
teresis cycles for 20 kN and 40 kN panels. Each
characteristic curve is just the constitutive law
of the respective panel: it is the one that should
be considered if the panel is subject to repeated
strain over time, as in the case of an earthquake.
This curve shows what was previously stated
about the hysteresis loops, namely that the panel
has an overall non-linear behavior due to the dis-
sipative phenomena.
The experimental curve differs from the nu-
merical one not only for the lower slope of the
initial part, but also for the lower value of the
Figure 15. Displacement transducers LVDT installed on the panels: a) global view and b) particular in
correspondence of load axis
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