Structural control systems
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Transcript of Structural control systems
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Structural Control
Systems
By:
Vineet Kothari
Assistant Professor
Civil Engineering Department
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Introduction
Ductile Concrete Moment
Resisting Frame Structure
(Parking Garage) that collapsed
during Northridge Earthquake
•Tremendous deformation Capacity in the Peripheral Columns
( Not Sufficiently Detailed to accommodate large Inelastic Deformations Demand…)
• So it is utmost important to have good and efficient structural control system.
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Dynamic Forces
SEISMIC WIND
Mass Lower Mass Higher
Stiffness Higher Stiffness Higher
Damping Higher Damping Higher
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WIND RESISTANT DESIGN
• Excitation is an applied Pressure or Force on the Facade
• Loading is Dynamic but Response is nearly Static for most Structures
• Structures deforms due to Applied force
• Deformations are monotonic (unidirectional)
• Structure is Designed to respond Elastically under Factored Loads
• The controlling Life Safety limit state is STRENGTH
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EARTHQUAKE RESISTANT DESIGN
• Excitation is an Applied Displacement at the Base
• Loading and Response are Truly Dynamic
• Structural Systems deforms as a result of Inertial Forces
• Structure is designed to respond Inelastically under Factored Loads
• Controlling Life Safety limit is DEFORMABILITY
• Enough Strength is provided to ensure that Inelastic deformation demands do
not exceed deformation Capacity.
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Structural Control Systems
• Energy absorption or dissipation devices
• by increasing stiffness (absorption)
• by improving dynamic performance (dissipation)
Methods to improve seismic response
conventional methods
1.Shear wall
2.Bracings Systems
3.Dual system
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Structural Control Systems
Modern methods
1. Passive control systems
2. Active Control systems
3. Semi-active control systems
4. Hybrid control systems
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Modern Methods
Base Isolation
• Introduces Flexibility in building
• Building is rested on flexible pads
• When earthquake strikes building does
not move
• It is suitable for hard soil only
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Types of Base Isolator
Elastomeric and Lead Rubber Bearing
• Frequently used for base isolation
• Made of rubber sandwiched together within steel
• Very stiff and strong in vertical direction
• Flexible in horizontal direction
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Types of Base Isolator
Spherical Sliding Isolation
• It uses bearing pads that have a curved surface and low
friction materials similar to Teflon
• During earthquake building is free to slide both
horizontally and vertically
• It returns to its original position as earthquake stops
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Base Isolation
Most
Effective
Least
Effective
• Structure with Stiff Soil
• Structure with Low Fundamental Period
(Low Rise Buildings)
• Structure with Soft Soil
• Structure with High Fundamental Period
(High Rise Buildings)
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Passive Energy Dissipation Devices
Passive energy Dissipation Devices
Viscous Fluid Damper
Visco-Elastic Damper
Metallic Damper
Tuned Mass Damper
Friction Damper
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Viscous Fluid Damper
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Visco-Elastic DamperEnergy Dissipation takes place due to shear deformation of material Sandwiched between
Steel Plates.
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Friction Damper• Friction provides Excellent mechanisms for Energy Dissipation and has
been used from many years in automotive Brakes to dissipate KineticEnergy of Motion.
• The friction damper consists of diagonal brace elements with a friction interface at
their intersection point, which are connected together by horizontal and vertical link
elements.
• These link arms ensure that when the load is applied to a device via the braces is
sufficient to initiate slip on tension diagonal, then compression diagonal will also slip
an equal amount in opposite direction.
• The friction resistance of the device requires a normal force on the sliding interface,
and this is achieved through a bolt at the intersection of the diagonal arms.
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Metallic DamperDissipation of energy input to a structure from an earthquake is through inelastic deformation of metals.
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Metallic Damper
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Thank YOU