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Pall
Friction Dampers
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Pall
Friction Dampers are simple and foolproof in construction. Basically,
these consist of series of steel plates, which are specially treated
to develop very reliable friction. These plates are clamped together
and allowed to slip at a predetermined load. Decades of research
and testing have led to perfecting the art of friction. Their performance
is reliable, repeatable and they possess large rectangular hysteresis
loops with negligible fade. Pall Friction Dampers are passive energy
dissipation devices and, therefore, need no energy source other
than earthquakes to operate it. They do not require any repair or
replacement after the earthquake and are always ready to do their
job.
Pall Friction Dampers are available for long slender tension-only
cross bracing, single diagonal tension-compression bracing and chevron
bracing. The damper for cross bracing is a unique mechanism. When
the brace in tension forces the damper to slip, the damper mechanism
forces the other brace to shorten and thus avoid buckling. In this
manner, the other brace is immediately ready to slip the damper
on reversal of cycle. These dampers have been used in 65 feet (22
m) long slender bracing. To avoid pounding at the expansion joints,
Pall Friction Connectors are custom made to accommodate bi-directional
movements.
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| Salient features |
- Their performance is independent of velocity
and hence exerts constant force for all future earthquakes,
design-based earthquake (DBE) or maximum credible earthquake
(MCE).
- A much greater quantity of energy can be dissipated
in friction than any other method involving the yielding of
steel plates, viscous or viscoelastic dampers. Therefore, fewer
Pall Friction Dampers are required to provide the required amount
of energy dissipation.
- In a typical un-damped structure, the inherent
damping is merely 1-5% of critical. With the introduction of
Pall Friction Dampers, structural damping of 20-50% of critical
can be easily achieved.
- Pall Friction Dampers are customized to suit
site conditions and allow greater adaptability than is possible
with other systems. These dampers can be bolted or welded into
place.
- Pall Friction Dampers provide a practical, economical
and effective approach for the design of structures to resist
major earthquakes. Low cost of Pall Friction Dampers suggests
wide application for all sectors of society - public, private
and developer.
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Quality
Control
Pall Friction Dampers meet a high standard of
quality control. Throughout the entire production process, stringent
quality control procedures ensure that the materials as well as
the finished product are of the highest order. Once assembled, every
Pall Friction Damper is load tested and its performance reviewed
by an engineer before shipment. |
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Benefits
- Introduction of high damping results in reduction
of forces and deflections.
- Added safety to building, contents and occupants.
- Performance based design at low cost.
- Saving in cost of new construction (1-2%) and
retrofit of existing buildings (30-60%).
- Saving in life cycle cost as damage is minimized.
- Saving in insurance premiums.
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