Geology Reference
In-Depth Information
Figure 4. Building with energy dissipaters
its design able to dissipate a great amount of the
seismic energy.
In summary, until now, the dissipaters that
have been developed are based on the following
principles:
•
Plastic deformation of metals
•
Friction
•
Elastomers with high damping capacity
•
Viscous fluid damping devices
The design of these devices is greatly influ-
enced by their force-displacement characteristics
and those of the building where they are installed.
One of the first buildings equipped with energy
dissipaters were the Twin Towers in New York.
These buildings incorporated many hundreds of
devices in the column-beam joints to increase
the structural damping for vibration control of
wind gusts.
Energy dissipaters present some advantages
respect to other control techniques such as base
isolation. They do not require either construction
or design techniques that differ from those used
in conventional buildings; energy dissipaters are
efficient in high and low rise buildings and their
unit cost is often low. Figure 4 shows a building
equipped with energy dissipaters installed in the
middle of the diagonals or at their connection
with the beams. These elements dissipate energy
through the relative displacements between the
floors.
evident that the energy dissipation takes place
only for drifts of a magnitude greater than that
activates the plastic behavior of the material. In
particular, metallic devices show a stable behavior
under cyclic loading, producing a large hysteretic
cycle that depends on the strength of the material.
Generally, the devices possess a large hysteretic
energy dissipation capacity in relation to their size.
However, the introduction of these devices in the
building increases the stiffness of the structure and
reduces the drifts that concentrate the damage on
the device. The limitation of these devices is that
the energy dissipation capability is only activated
after the activation of large excursions into the
inelastic range and, as a result, they are not effec-
tive for small vibrations of the drift that produces
the yield in the material composing the device.
Hysteretic Dissipaters
As part of the passive control techniques, special
attention is given to devices that help to dissipate
the energy entering a structure during an earth-
quake, through the activation of hysteresis loops
in the material of the device itself (Skinner et al.
1980, Bozzo et al. 1998), thus avoiding plastic
action of structural elements. Therefore, it is
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