experimental development and analysis of a high force / volume extrusion damper gw rodgers, c...
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Experimental Development and Analysis of Experimental Development and Analysis of a High Force / Volume Extrusion Dampera High Force / Volume Extrusion Damper
GW Rodgers, C Denmead, N Leach, JG Chase & John B ManderGW Rodgers, C Denmead, N Leach, JG Chase & John B Mander
‘‘Energy Dissipation Without Damage’Energy Dissipation Without Damage’
Putty
Device fixed to re-bar cage at each end and embedded in concrete for containment
Damage to concrete and yielding of re-bar
Objectives: - To eliminate yielding in the critical reinforcing bars - To absorb more energy than a ductile concrete system
Problem:Problem:
Solution:Solution:
Requires expensive repair or retrofit
Does not require expensive repair
Must be small enough to fit where traditional
dampers do not!
And deliver forces just as large!
Other Possible ApplicationsOther Possible Applications
Seismically Vulnerable Bridge Piers
Steel jointsSteel joints Reinforced concrete jointsReinforced concrete joints Bridge decksBridge decks Tuned mass dampersTuned mass dampers Base isolationBase isolation
Single or double bulge extrusion damper fixed to column
Steel Beam
Steel Beam
Steel Column
Dissipative rocking with no damage
Gap transmits joint rotation to damper instead of damage
Direct Placement into Steel Joints
RequirementsRequirements
High force capacityHigh force capacity = High dissipation = High dissipation Only 3-10 large response cycles per big earthquakeOnly 3-10 large response cycles per big earthquake
Small device volumeSmall device volume Tight constraints for typical structural connections - Universal Tight constraints for typical structural connections - Universal
column sections nominally 350mm deep – W14 in American Codescolumn sections nominally 350mm deep – W14 in American Codes
Maximum energy dissipation per cycleMaximum energy dissipation per cycle ““Square” hysteresis loopSquare” hysteresis loop
GoalGoal:: Dissipate energy in the device every cycle rather Dissipate energy in the device every cycle rather than by damage to structural connectionsthan by damage to structural connections
Sinusoidal Input
• 500kN compression testing device
• Quasi-Static
• DARTEC 10,000kN dynamic test system
Lead
Fixed in Place
Test MethodTest Method
• 40mm bulge• Quasi-static test• 100kN peak force, 50kN average• Not repeatable• Trailing void formation ~10%
40 mm diameter bulge with un-pre-stressed lead
-150
-100
-50
0
50
100
150
-20 -10 0 10 20 30
Displacement (mm)
Fo
rce (
kN
)
Results without pre-stressResults without pre-stress
Device coring trailing void
Peak force only in “new” material
Bulge Diameter of 40mm
-200
-150
-100
-50
0
50
100
150
200
-5 5 15 25 35 45 55
Displacement (mm)
Lo
ad
(k
N)
Bulge Diameter of 50mm
-300
-200
-100
0
100
200
300
-5 5 15 25 35 45 55
Displacement (mm)
Load
(kN
)
Results with pre-stressResults with pre-stress
• Air voids decreased by 3-5x
• ‘Squarer’ hysteresis loops
for max energy dissipation
• Repeatable results
• Small decrease in force still
due to air voids, but much less
• Air voids same ~2-3% volume
• 40mm bulge has longer void as
smaller bulge than 50mm as it
is about void volume
50mm Bulge Diameter
40mm Bulge Diameter
Experimental RelationshipsExperimental Relationships• Variation in reported and experimental relationships – linear and polynomial• Linear relationship in tested region• Likely the relationship would become exponential
0
100
200
300
400
500
600
700
800
900
1000
30 35 40 45 50 55 60 65 70
Bulge diameter (mm)
Fo
rce
(k
N)
Reported relationship
Least square fit
Force/Bulge Diameter Relationship
Friction Shaft Yield
Experimental RelationshipsExperimental Relationships
• Ratio makes relationship device independent
• Linear relationship
• Wider variety of devices
• Relationship used to estimate design force
Can be readily used for new device designs
0
50
100
150
200
250
300
350
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Face Area bulge/Area cylinder
Forc
e (k
N)
Relationship between ratio of bulge areato cylinder area and Force
Exhibits Mohr-Coulomb Behaviour
ebuoshaftDD AAD lg
Structural ImpactStructural ImpactSpectral Response decreases with increasing damper size
• Reduced magnitude of structural response and damage• Multiple earthquake suites (3x20=60) of probabilistically scaled earthquake records – near field and far field ground motions
Reduction in response with increasing damper size
Reduction in response with increasing damper size
El Centro Response Spectra
Structural ImpactStructural ImpactReduction Factors• Design spectra divided by the spectra with added extrusion damping• Indicates the magnitude of the achieved reduction in response
Reduction factors
increase with increasing
damper size
Structural Design ImpactStructural Design Impact
• Split the spectra into 3 regions based upon existing bifurcation points• Use linear regression analysis and linear interpolation• Obtain equations to estimate damping reduction factors• Enable use in structural design analyses
Multiple Equation Regression Analysis
ConclusionsConclusions
Importance of pre-stress in repeatable device behaviour and Importance of pre-stress in repeatable device behaviour and maximum energy dissipation identifiedmaximum energy dissipation identified
Full-scale 300kN+ prototype created and testedFull-scale 300kN+ prototype created and tested
Final device design underwent proof-of-concept testing over entire Final device design underwent proof-of-concept testing over entire speed rangespeed range
Analytical design space characterised and device independentAnalytical design space characterised and device independent Results not same compared to studies reported in the literatureResults not same compared to studies reported in the literature
Comprehensive theoretical simulation of device placement in a Comprehensive theoretical simulation of device placement in a structure shows significant impact on responsestructure shows significant impact on response
Future work requires some minor modifications but the concept is Future work requires some minor modifications but the concept is proven for multiple devicesproven for multiple devices