1、Experimental Development and Analysis of a High Force / Volume Extrusion Damper,GW Rodgers, C Denmead, N Leach, JG Chase & John B Mander,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,
2、Objectives: - To eliminate yielding in the critical reinforcing bars- To absorb more energy than a ductile concrete system,Problem:,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 a
3、s large!,Other Possible Applications,Seismically Vulnerable Bridge Piers,Steel joints Reinforced concrete joints Bridge decks Tuned mass dampers Base isolation,Single or double bulge extrusion damper fixed to column,Steel Beam,Steel Beam,Steel Column,Dissipative rocking with no damage,Gap transmits
4、joint rotation to damper instead of damage,Direct Placement into Steel Joints,Requirements,High force capacity = High dissipation Only 3-10 large response cycles per big earthquakeSmall device volume Tight constraints for typical structural connections - Universal column sections nominally 350mm dee
5、p W14 in American CodesMaximum energy dissipation per cycle “Square” hysteresis loopGoal: Dissipate energy in the device every cycle rather than by damage to structural connections,Sinusoidal Input,500kN compression testing deviceQuasi-StaticDARTEC 10,000kN dynamic test system,Lead,Fixed in Place,Te
6、st Method,40mm bulgeQuasi-static test100kN peak force, 50kN averageNot repeatableTrailing void formation 10%,Results without pre-stress,Device coring trailing void,Peak force only in “new” material,Results with pre-stress,Air voids decreased by 3-5xSquarer hysteresis loopsfor max energy dissipationR
7、epeatable results,Small decrease in force stilldue to air voids, but much lessAir voids same 2-3% volume40mm bulge has longer void as smaller bulge than 50mm as itis about void volume,50mm Bulge Diameter,40mm Bulge Diameter,Experimental Relationships,Variation in reported and experimental relationsh
8、ips linear and polynomialLinear relationship in tested regionLikely the relationship would become exponential,Force/Bulge Diameter Relationship,Friction,Shaft Yield,Experimental Relationships,Ratio makes relationship device independentLinear relationshipWider variety of devicesRelationship used to e
9、stimatedesign force,Can be readily used for new device designs,Relationship between ratio of bulge area to cylinder area and Force,Exhibits Mohr-Coulomb Behaviour,Structural Impact,Spectral Response decreases with increasing damper sizeReduced magnitude of structural response and damageMultiple eart
10、hquake 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 Impact,Reduction FactorsDesign spectra divided by t
11、he spectra with added extrusion dampingIndicates the magnitude of the achieved reduction in response,Reduction factors increase with increasing damper size,Structural Design Impact,Split the spectra into 3 regions based upon existing bifurcation pointsUse linear regression analysis and linear interp
12、olationObtain equations to estimate damping reduction factorsEnable use in structural design analyses,Multiple Equation Regression Analysis,Conclusions,Importance of pre-stress in repeatable device behaviour and maximum energy dissipation identifiedFull-scale 300kN+ prototype created and testedFinal
13、 device design underwent proof-of-concept testing over entire speed rangeAnalytical design space characterised and device independent Results not same compared to studies reported in the literatureComprehensive theoretical simulation of device placement in a structure shows significant impact on responseFuture work requires some minor modifications but the concept is proven for multiple devices,
