Energy Dissipation System(Dampers)
• Mechanical system which dissipate earthquake
energy into specialized devices which deforms or
yield during earthquake.
• They enhance energy dissipation in a structure to
which they are installed so that the structure has to
resist lesser amount of earthquake forces.
• They are not used to support the structure.
• When seismic energy is transmitted through
them, dampers absorb part of it, and thus damp
the motion of the building.
Behavior of Building with and without dampers
• When ground seismic waves reach up and start
to penetrate a base of a building and the base of
the building starts moving.
• Due to inertia the building continue to remain in
the previous position.
• Due to this the building suffers distortion and the
distortion wave travels along the height of the
• Continue shaking of the base causes the
building to undergo series of oscillations which
ultimately results in collapse of building.
• To avoid such a circumstance dampers are
• Dampers dissipate the wave energy inside a
superstructure caused by seismic waves and
thus controlling the oscillations of the building
• By proper configuration of lateral resisting
system, the earthquake energy is directed
towards these devices located within the lateral
resisting elements, to intercept this energy.
• Due to the earthquake induced mechanical
energy in the system is transformed into thermal
energy within these devices
• These devices enhance the damping
characteristics of the structure and
consequently the amplitude of the motion of
the structure is damped, thereby reducing the
forces on structural members.
• These may be provided in isolation or
coupled with rubber pads in series or parallel.
Types of Dampers
Hydraulic Dampers(oleodynamic devices)
• Used with objective of permitting slowly developing
displacements due to thermal movements, but
limiting the response under dynamic actions.
• These system dissipate energy by forcing a fluid
through an orifice.
• The fluid may be oil or very high molecular weight
• They constitute a piston moving axially in
the polymer, inside the cylinder.
• They may also constitute a piston moving
in every direction in viscous elastomers
like silicon or bitumen.
• Oil dampers require frequent maintenance so
not commonly used.
Electro- Rheological Fluid Dampers(ERF-D)
• Passive fluid dampers including friction type
• Operate under shear flow.
• Fluid viscous damping reduces stress and
deflection because the force from damping is
completely out of phase with stresses due to
• This is because damping force varies with
• Other types of dampers, such as yielding
elements, friction devices, plastic hinges and
visco- elastic elastomers, do not vary their
output with velocity.
• Hence they can increase column stress while
• Utilize the hysteretic behaviour of metals in the
• These can be fabricated from steel, lead or
spherical shape memory alloys.
• These systems are referred to as amplitude
• Since the amount of energy dissipated,
which is hysteretic in nature, is usually
proportional to force and displacements.
• It is most often located within the structural
lateral load resisting elements such as
• Fabricated from round steel bars for
• energy is dissipated by inelastic
deformation of the rectangular steel frame
in the diagonal direction of the tension
• The friction surfaces are clamped with
• It exhibit perfect rectangular hysteretic
• Referred to as displacement- dependent
systems, since the amount of energy
dissipated is proportional to displacement.
• Contact surfaces used are lead- bronze
against stainless steel or teflon against
stainless steel. 17
Shape memory alloys
• Also known as smart alloys, are metals that,
after being strained, revert back to their original
• These enable large forces and movement
actuation, as they can recover from large strain
• They have capability of dissipating energy
without incurring damage, as in case of steel
dampers, when they yield.
• Alloys used are NiTi, CuZnAl and CuAlNi.