Guided by:
Dr. M.K.Shrimali
Dr. S.D. Bharti


Submitted by:
MAHESH CHAND SHARMA
M.TECH. –III SEM (2011-12)
(2010PST116)
Department of Structural Engineering
Malaviya National Institute of Technology Jaipur

Civil engineering structures located in
environments where earthquakes or large wind
forces are common will be subjected to serious
vibrations during their lifetime. These vibrations
can range from harmless to severe with the later
resulting in serious structural damage and
potential structural failure.
 The Traditional Technique of a
seismic Design
( increase the stiffness of structures by enlarging the section
of columns, beams, shear walls, or other elements)
 Modern Approach through
Structural Controls
(by installing some devices, mechanisms, substructures in
the structure to change or adjust the dynamic performance
of the structure)

Control systems add damping to the structure
and/or alter the structure’s dynamic properties.
Adding damping increases the structural energydissipating capacity, and altering structural
stiffness can avoid resonance to external
excitation, thus reducing structural seismic
response.
1.Passive control systems
2.Active Control systems
3.Semi-active control systems
4.Hybrid control systems

The passive control system does not require an
external power source and being utilizes the
structural motion to dissipate seismic energy or
isolates the vibrations so that response of
structure can be controlled
 1. Base Isolation
 2. Passive Energy Dissipating (PED)
Devices
A building mounted on a material with low
lateral stiffness, such as rubber, achieves a
flexible base.
 During the earthquake, the flexible base is able
to filter out high frequencies from the ground
motion and to prevent the building from being
damaged or collapsing
- deflecting the seismic energy and
- absorbing the seismic energy

Conventional Structure
Base-Isolated Structure
http://www.earthquakeprotection.com.
 Elastomeric Bearings:
-Low-Damping Natural or Synthetic Rubber Bearing
- High-Damping Natural Rubber Bearing
- Lead-Rubber Bearing
(Low damping natural rubber with lead core)
 Sliding Bearings
- Flat Sliding Bearing
- Spherical Sliding Bearing
Major Components:
- Rubber Layers: Provide
lateral flexibility
- Steel Shims: Provide
vertical stiffness to
support building weight
while limiting lateral
bulging of rubber
- Lead plug: Provides
source
of
energy
dissipation

http://www.earthquakeprotection.com.

Linear behavior in shear for shear
strains up to and exceeding 100%.

Damping ratio = 2 to 3%


http://www.earthquakeprotection.com.
Advantages:
- Simple to manufacture
- Easy to model
- Response not strongly sensitive to
rate of loading, history of loading,
temperature, and aging.
Disadvantage:
-Need supplemental damping system
• Damping increased by adding extra-fine carbon black, oils or resins,
and other proprietary fillers
• Maximum shear strain = 200 to 350%
• Damping ratio = 10 to 20% at shear strains of 100%
• Effective Stiffness and Damping depend on:
- Elastomer and fillers
- Contact pressure
- Velocity of loading
- Load history (scragging)
- Temperature
http://www.earthquakeprotection.com.
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damping properties can be improve
by plugging a lead core into the
bearing
damping of the lead-plug bearing
varies from 15% to 35%.
The Performance depends on the
imposed lateral force
The hysteretic damping is developed
with energy absorbed by the lead
core.
Maximum shear strain = 125 to 200%
,
Design of structures with seismic isolation, in The Seismic Design Handbook , 2nd edition

The imposed lateral force is
resisted by the product of the
friction coefficient and the
vertical load applied on the
bearing

Mechanical devices to dissipate or absorb a portion of
structural input energy, thus reducing structural response
and possible structural damage.
•
Metallic Yield Dampers
•
Friction Dampers
• Visco-elastic Dampers
•
Viscous Fluid Dampers, And
•
Tuned Mass Dampers And Tuned Liquid Dampers.

Metallic yield damper:
relies on the principle
that the metallic device
deforms plastically, thus
dissipating vibratory
energy
http://www.earthquakeprotection.com.

here friction between
sliding faces is used to
dissipate energy
Instructional Material Complementing FEMA 451,

Visco-elastic (VE)
dampers utilize high
damping from VE
materials to dissipate
energy through shear
deformation.
Such materials include
rubber, polymers, and
glassy substances.
http://www.earthquakeprotection.com.

A viscous fluid damper
consists of a hollow
cylinder filled with a
fluid. As the damper
piston rod and piston
head are stroked, The
fluid flows at high
velocities , resulting in
the development of
friction
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A mass that is connected to a
structure by a spring and a
damping element without
any other support,in order to
reduce vibration of the
structure
Tuned liquid dampers are
similar to tuned mass
dampers except that the
mass-spring-damper system
is replaced by the container
filled with fluid
Tuned liquid dampers
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Tuned mass dampers
In the active control, an external source of energy is used to
activate the control system by providing an analog signal to
it. This signal is generated by the computer following a
control algorithm that uses measured responses of the
structure

Active Mass Damper Systems

Active Tendon Systems

Active Brace Systems

It evolved from TMDs
with the introduction of
an active control
mechanism.
http://www.earthquakeprotection.com.

Active tendon control
systems consist of a set
of pre-stressed tendons
whose tension is
controlled by electrohydraulic
servomechanisms
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
It compromise between the passive and active
control devices.

the structural motion is utilized to develop the
control actions or forces through the adjustment
of its mechanical properties

The action of control forces can maintained by using
small external power supply or even with battery
1.Stiffness control devices
2.Electro-rheological dampers
3.Magnetorhelogical dampers
4.Friction control devices
5.Fluid viscous dampers
6.Tuned mass dampers
7.Tuned liquid dampers

ER fluids that contain
dielectric
particles
suspended within
nonconducting viscous fluids

When the ER fluid is
subjected to an electric field,
the
dielectric
particles
polarize and become aligned,
thus offering resistance to
the flow.
http://www.earthquakeprotection.com.
 Modify:
- the stiffness
-the
natural
vibration
characteristics
 So
create a nonresonant condition
during earthquake

MR fluid contains micron-size,
magnetically
polarizable
particles dispersed in a viscous
fluid

When the MR fluid is exposed
to a magnetic field, the
particles in the fluid polarize,
and the fluid exhibits viscoplastic behavior, thus offering
resistance to the fluid flow.
http://www.earthquakeprotection.com.

Combine controls system together
› Passive + Active
› Passive + Semi-Active
 Smart base-isolation
Reduce external power requirement
 Improve reliability

› When loss of electric during earthquake, hybrid
control can act as a passive control

Reduce construction and maintenance costs due
to active or semi-active
1. Agrawal, A.K. and ang, J.N., Hybrid control of seismic response using nonlinear
output feedback, in Proceedings of the Twelfth ASCE Conference on Analysis
and
Computation, Cheng, F.Y. (ed.), 1996, p. 339.
2. Aiken, I.D. and Kelly, J.M., Comparative study of four passive energy dissipation
systems, Bulletin of New Zealand National Society of Earthquake Engineering,
25, 175, 1992.
3. Aiken, I.D. et al., Testing of passive energy dissipation systems, EERI Earthquake
Spectra, 9, 335, 1993.
4. Aizawa, S. et al., An experimental study on the active mass damper, in
Proceedings
of the Ninth World Conference on Earthquake Engineering, International
Association for Earthquake Engineering, Tokyo, 1988, V, p. 87l.
5. Akbay, A. and Aktan, H.M., Actively regulated friction slip braces, in
Proceedings
of the Sixth Canadian Conference on Earthquake Engineering, Toronto, Canada,
1991, p. 367.