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the different requirements. The fundamental idea
was to obtain a high reduction of the effects of an
earthquake on a building utilizing a material such
as aluminum with a low yielding limit that could
dissipate a good amount of seismic energy for hys-
teresys. The first device consists in a shear panel
composed of a central aluminum plate and two
steel side plates (Foti et al. 1999, Foti et al. 2000).
A series of shaking-table tests were performed on
this preliminary aluminum-steel device (Bairrao
R. et, al., 2000) and a good behavior but also some
critical points were observed. In particular, the
efficacy of the panel was sensibly reduced by the
difficulty in assuring a correct load transmission
between plates of steel and aluminum.
Starting from these observations, Fe360 steel
and a 1000 series aluminum alloy plate were cho-
sen respectively for the outside plates and for the
central device (Diaferio et al. ECSC 2008, Foti
et al. 2010). A low yield stress and a large plastic
range, increasing the extent of yielding even at low
loads (Table 1), characterize the 1000 series alloys.
The proposed configuration provides adequate
stiffness to increase the limit of instability in the
shear panel. This latter feature is important to
reduce the possibility of out-of-plane instability
of the device. Steel plates provide the necessary
stiffness to the panel, while the aluminum is the
element that dissipates energy. The steel plates
have rectangular openings (Figure 5), from which
the central aluminum plate emerges for a few
millimeters. This solution ensures that the panel
behaves as desired, particularly assuring that the
load is transmitted between the aluminum and
steel, avoiding the possibility of slippage. This
behavior is achieved in part with the aluminum
protrusions into the openings of the steel panels,
which provide a barrier to slipping. Moreover, all
the three plates are connected through bolts to
enhance connectivity between the plates. The
design of the device obviously took into account
how it has to be connected to the structure to be
protected. To facilitate the inclusion of the panel
in different structures, a standard configuration
shown in Figure 6 has been designed where two
diagonal bracings are bolted to the frame and
welded to a plate where the device will be installed.
Maximum dimension of the area provided for the
panel is 470x600 mm. This particular configura-
tion will be assumed in the following for the
panel dimensioning and for the experimental test.
Optimum Design of the Device
The considerations reported before allowed to
define the standard configuration of device, but
were not exhaustive to define the geometrical
configuration of the panel, that is the definition
of the design parameters showed in Figure 5. This
problem represents a classical case in which a
structural optimization procedure can help to de-
fine the final geometry of the device. To improve
the dissipation behavior of the device, the shape
design of the dissipater was thought to be obtained
from an optimization study with the principal aim
to get the maximum amount of energy dissipated
by the device during a seismic event.
The optimization procedure consists in assign-
ing a possible form and shape to the initial panel,
while some dimensions and characteristics have
been maintained in a parametric form. Literature
is very rich about optimization procedure starting
from simple linear approach to more sophisticated
and non linear approach (Kirsch 1993, Spillers and
MacBain 2009). In this case, the authors choose
to consider an optimization procedure integrated
Table 1. Mechanical properties of steel and alu-
minum utilized in the device
Materials properties
Fe360
Series 1000
Al
σ
y
Yielding stress [N/mm
2
]
235
30
Ultimate tensile stress
[N/mm
2
]
σ
R
360
90
A
Rupture elongation [%]
26
40
E
Young modulus [N/mm
2
]
206000 70000
H
Plastic modulus [N/mm
2
]
20000
5000
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