Vibration Control and Vibration Control and Benchmark Problems on Bridges Benchmark Problems on Bridges Suhasini Madhekar Suhasini Madhekar College of Engineering Pune College of Engineering Pune Faculty Development Program on Faculty Development Program on Fundamentals of Structural Dynamics and Application to Fundamentals of Structural Dynamics and Application to Earthquake Engineering Earthquake Engineering 12 12 th th December 2015 December 2015 Sanjay Sanjay Ghodawat Ghodawat Group of Institutions Group of Institutions Atigre Atigre, Kolhapur , Kolhapur 1
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Vibration Control and Vibration Control and
Benchmark Problems on BridgesBenchmark Problems on Bridges
Suhasini Madhekar Suhasini Madhekar
College of Engineering PuneCollege of Engineering Pune
Faculty Development Program onFaculty Development Program on
Fundamentals of Structural Dynamics and Application to Fundamentals of Structural Dynamics and Application to
Earthquake EngineeringEarthquake Engineering
1212thth December 2015December 2015
Sanjay Sanjay GhodawatGhodawat Group of InstitutionsGroup of Institutions
AtigreAtigre, Kolhapur, Kolhapur 11
Golden Gate Bridge, USAGolden Gate Bridge, USA
Firth of Forth Bridge, ScotlandFirth of Forth Bridge, ScotlandSunshine skyway Bridge, USASunshine skyway Bridge, USA
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Bridges on Konkan RailwaysBridges on Konkan Railways
Catastrophic Failures of ‘LCatastrophic Failures of ‘Lifeline’ifeline’ structure !!!structure !!!
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Catastrophic Failures..Catastrophic Failures..
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Seismic Design Approach
Traditional
••Fixed to groundFixed to ground
••Amplification of Amplification of
AccelerationAcceleration
With controllers
••Seismic demand reducedSeismic demand reduced
••Reduced deck Reduced deck
accelerations and driftsaccelerations and driftsAccelerationAcceleration
0.2 0.2 ≤≤ T T ≤ ≤ 1.2 sec. 1.2 sec. -- Close to the preClose to the pre--dominant periods of dominant periods of
earthquake induced ground accelerations : results in earthquake induced ground accelerations : results in
amplification of response. amplification of response.
Bridges: Extremely vulnerable to damage Bridges: Extremely vulnerable to damage –– Relatively large Relatively large Bridges: Extremely vulnerable to damage Bridges: Extremely vulnerable to damage –– Relatively large Relatively large
deck mass supported by slender columns. Large deck mass supported by slender columns. Large
displacements displacements -- large shear forces in the piers large shear forces in the piers
Effort of protection of bridges against earthquakes: Focused Effort of protection of bridges against earthquakes: Focused
on minimizing shear forces transmitted to piers.on minimizing shear forces transmitted to piers.
Vibration Control of StructuresVibration Control of Structures
�� Dynamic loading on Bridges due Dynamic loading on Bridges due to Earthquakes, to Earthquakes, highhigh--wind, wind,
��Benchmark Highway Bridge (Agrawal et al., 2005)Benchmark Highway Bridge (Agrawal et al., 2005)
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Choice of Control SystemChoice of Control System
Important Features of the structure Important Features of the structure
Height, plan dimensions, symmetry / asymmetry Height, plan dimensions, symmetry / asymmetry
of the buildingof the building
Total span of the bridge, continuous / simply Total span of the bridge, continuous / simply Total span of the bridge, continuous / simply Total span of the bridge, continuous / simply
supported spanssupported spans
Number of continuous spansNumber of continuous spans
Seismic Zone Seismic Zone
Frequency of vibration: Past recordsFrequency of vibration: Past records4141
Benchmark Highway BridgeBenchmark Highway Bridge
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Case I: Bridge deck fixed to outrigger and isolated at the Case I: Bridge deck fixed to outrigger and isolated at the
abutments (16 control devices); Case II: Bridge deck also abutments (16 control devices); Case II: Bridge deck also
isolated at the outrigger (20 control devices) isolated at the outrigger (20 control devices)
Located near two major faults (~ 20 km) : strong seismic Located near two major faults (~ 20 km) : strong seismic
considerationsconsiderations
Benchmark Highway BridgeBenchmark Highway Bridge
considerationsconsiderations
Two spanTwo span--four lane continuous PC Highway bridge with four lane continuous PC Highway bridge with
skewed abutmentsskewed abutments
Six real biSix real bi--directional earthquake ground motionsdirectional earthquake ground motions
Evaluation criteria : Deck displacement and acceleration, Pier Evaluation criteria : Deck displacement and acceleration, Pier
base shear etc.base shear etc. 4343
Phase I: Bridge deck fixed to outrigger and isolated at the abutments.
(control devices =16)
Phase II: Bridge deck also isolated at the outrigger (control devices=20)
Located near two major faults (~ 20 km)
Two span - four lane continuous Highway bridge with abutments skewed
at 330
Bridge deck : 3 cells PC box girder , Central bent : PC outrigger
Total mass of the bridge = 4,237,544 kg , Mass of deck = 3,278,404 kg
Benchmark Highway BridgeBenchmark Highway Bridge
Total mass of the bridge = 4,237,544 kg , Mass of deck = 3,278,404 kg
Actual bridge : At each abutment : 4 traditional non-seismic elastomeric
pads and 4 viscous fluid dampers
Effect of Soil structure interaction is considered
–– Base shear Base shear –– Shear at deck level Shear at deck level
–– Overturning moment Overturning moment –– Moment at deck levelMoment at deck level
–– Cable tensionCable tension
–– Deck displacement at abutmentDeck displacement at abutment
�� Normed Responses (Normed Responses (JJ77
–– JJ1111
))�� Normed Responses (Normed Responses (JJ77
–– JJ1111
))
–– Base shear Base shear –– Shear at deck level Shear at deck level
–– Overturning moment Overturning moment –– Moment at deck levelMoment at deck level
–– Cable tensionCable tension
�� Control Strategy (Control Strategy (JJ1212
–– JJ1818
))
–– Peak control force and device strokePeak control force and device stroke
–– Peak and total power requiredPeak and total power required
–– Number of control devices and sensorsNumber of control devices and sensors
Seismic Control System Seismic Control System
Using MR DampersUsing MR Dampers
� Sensors
– Five accelerometers
– Four displacement transducers– Four displacement transducers
– 24 force transducers for measuring control forces
� Control Devices
– 24 MR dampers (capacity: 1000 kN/each)
Dynamic Model Dynamic Model s of s of MR DampersMR Dampers
Models for small-scale
dampers
Bingham model (Stanway
et al. 1985, 1987)et al. 1985, 1987)
Simple Bouc-Wen model
(Spencer et al. 1997)
Model for large-scale damper
Modified Bouc-Wen model
(Spencer et al. 1997)24 MR Dampers:1000 kN Capacity
Optimized Parameters of Dynamic Model Optimized Parameters of Dynamic Model
for MR Dampersfor MR Dampers
Dynamic Degrees of FreedomDynamic Degrees of Freedom
Reduced Order Model
with 30 States
Control Strategy for Semiactive ControlControl Strategy for Semiactive Control
TimeTime--History History Response : Base Response : Base Shear Shear Force Force
• El Centro earthquake: 71% reduction in peak
kNkN
kNkN
• Gebze Turkey earthquake: 64% reduction in peak
• Mexico City earthquake: 54% reduction in peakkNkN
First generation structures First generation structures : without any code / systematic : without any code / systematic
proceduresprocedures
Design and analysis procedure for Design and analysis procedure for Second Generation Second Generation
StructuresStructures is available. Still catastrophic failures are is available. Still catastrophic failures are
ConclusionsConclusions
observed in severe earthquake attacks. observed in severe earthquake attacks.
Based on the performance of conventionally designed Based on the performance of conventionally designed
structures, there is a structures, there is a need forneed for Third Generation structuresThird Generation structures. .
Practically : use of isolators (LRB and FPS) and limited Practically : use of isolators (LRB and FPS) and limited
applications (Viscous and MR) of dampers in the world. applications (Viscous and MR) of dampers in the world.
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ConclusionsConclusions
Vibrations : Seismic and windVibrations : Seismic and wind
Experimental validation of devices is necessaryExperimental validation of devices is necessary
Inclusion of clauses in IS codesInclusion of clauses in IS codes
Newly developed control devices can be implemented in Newly developed control devices can be implemented in Newly developed control devices can be implemented in Newly developed control devices can be implemented in
constructions.constructions.
Devices can be used for retrofitting of existing structures. Devices can be used for retrofitting of existing structures.
Commonly used isolators : LRB, FPSCommonly used isolators : LRB, FPS
Commonly used dampers: Viscous dampers, Commonly used dampers: Viscous dampers, ViscoVisco--elastic elastic