1. Second International Conference on Construction Materials and Structures (ICCMS-2022)
SEISMIC RESITANT DESIGN OF STRUCTURES
PRESENTED BY
PASSIVE CONTROL SYSTEM IN EARTHQUAKE STRUCTURES
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INTRODUCTION
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.
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SEISMIC PROTECTION OF STRUCTURES
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
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BASIC PRINCIPLES OF SEISMIC RESPONSE CONTROL
Control systems add damping to the structure and/or alter the structure's
dynamic properties. Adding damping increases the structural energy-
dissipating capacity, and altering structural stiffness can avoid resonance
to external reducing structural seismic response.
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STRUCTURAL CONTROL SYSTEMS
Passive control system
Active control system
Semi active control system
Hybrid control system
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PASSIVE 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
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The passive control devices
• Base isolation
• Passive energy dissipating (PED)
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BASE ISOLATION
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 a
- absorbing the seismic energy
BEHAVIOUR OF STRUCTURE WITH BASE
ISOLATION SYSTEM
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VARIOUS TYPE OF BASE ISOLATION
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
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VARIOUS TYPES OF BASE ISOLATION
ELASTOMERIC BEARINGS:
• Low Damping Natural Or Synthetic Rubber Bearing
• High Damping Natural Bearing
• Lead Rubber Bearing
SLIDING BEARINGS
• Flat Sliding Bearings
• Spherical Sliding Bearings
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ELASTOMERIC BEARINGS
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
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LOW DLOW DAMPING NATURAL OR SYNTHETIC RUBBER BEARINGS
LOW DAMPING NATURAL OR SYNTHETIC RUBBER BEARINGS
OR SYNTHETIC RUBBER BEARINGS
Linear behavior in shear for shear strains up to and
exceeding 100%.
Damping ratio = 2 to 3%•
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
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HIGH-DAMPING NATURAL RUBBER BEARINGS:
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
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LEAD-RUBBER BEARINGS
• Damping properties can be improve
by plugging a lead core into the
bearings damping of the lead-plug
bearing varies from 15% to 35%.
• The Performance depends on the
imposed lateral force Steel
Lamination Lead Rubber
• The hysteretic damping is developed
with energy absorbed by the lead
core.
• The maximum shear strain = 125%to
200%
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SLIDING BEARINGS
• The imposed lateral force is resisted by the
product of the friction coefficient and the
vertical load applied on the bearing
• Articulated slide
• Teflon coated spherical
• surfaceStainless steel base
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PASSIVE ENERGY DISSIPATING DEVICES 1 (PED)
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.
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METTALIC YEILD DAMPERS
Metallic yield damper:
• relies on the principle the metallic
device deforms plastically, thus
dissipating vibratory energy
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FRICTION DAMPERS
Bracing members
• here friction between sliding faces
is used to dissipate energy
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VISCO ELASTIC DAMPERS
• Visco Elastic dampers utilize high
damping from ve materials to
dissipate energy through shear
deformtion.
• Such materials include rubber
,polymers and glassy substances
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VISCOUS FLUID DAMPERS
• A viscous fluid damper consists
of a hollow cylinder filled with a
fluid .As the damper piston rod
and piston and piston head
stroked, The fluid flows at high
velocities ,resulting in the
development of friction .
