Seismic Testing of an Isolated Scale-Model Bridge Structure with an Adaptive Passive Negative Stiffness Device N. Attary and M.D. Symans Rensselaer Polytechnic Institute S. Nagarajaiah and D.T.R. Pasala Rice University A.M. Reinhorn, M.C. Constantinou, and A.A. Sarlis University at Buffalo D. Taylor Taylor Devices, Inc. 1 2012 Quake Summit, Boston, MA Session 4, Base Isolation/Energy Dissipation July 11, 2012
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Seismic Testing of an Isolated Scale-Model Bridge Structure with an Adaptive Passive Negative Stiffness Device N. Attary and M.D. Symans Rensselaer Polytechnic.
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Seismic Testing of an Isolated Scale-Model Bridge Structure with an Adaptive Passive
Negative Stiffness DeviceN. Attary and M.D. Symans
Rensselaer Polytechnic Institute
S. Nagarajaiah and D.T.R. Pasala
Rice University
A.M. Reinhorn, M.C. Constantinou, and A.A. Sarlis
University at Buffalo
D. Taylor
Taylor Devices, Inc.
2012 Quake Summit, Boston, MASession 4, Base Isolation/Energy Dissipation
July 11, 2012
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NEESR-SG: Development of Next Generation Adaptive Seismic Protection Systems
Satish NagarajaiahProfessor
Civil & Mechanical Eng.Rice University
Michael SymansAssociate Professor
Civil EngineeringRensselaer Polytechnic Institute
Andrei ReinhornProfessor
Civil EngineeringUniversity at Buffalo
Michael ConstantinouProfessor
Civil EngineeringUniversity at Buffalo
Jian ZhangAssistant Professor
Civil EngineeringUniv. of Calif. Los Angeles
Douglas TaylorPresident, Taylor Devices, Inc.
Mechanical EngineeringTaylor Device Inc.
Research supported by National Science Foundation CMMI Grant No. 0830391 (NEESR - Network for Earthquake Engineering Simulation Research)
Project Team
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Outline• Seismic Protection Systems for Bridges
• Concept of Negative Stiffness
• Development of Mechanical Negative Stiffness Device
• Implementation of Negative Stiffness Device within a Quarter-Scale Bridge Structure
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Advanced Seismic Protection Systems for Bridges
• Patten (1998)Semi-active control using variable-orifice fluid damping/stiffness device (implemented in highwaybridge in Oklahoma for vibration control)
• Sahasrabudhe and Nagarajaiah (2005)
Semi-active control of isolated bridge using:– Magnetorheological (MR) dampers– Variable stiffness devices
Small-scale bridge model
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Improved Seismic Performance via Combined Weakening and Damping
Source: Reinhorn et. al. (2002)
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Concept of Negative Stiffness Force develops in same direction as imposed force
Positive vs. Negative StiffnessAdding Positive/Negative Stiffness to a Basic
System with Positive Stiffness
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Working Principle of Negative Stiffness and Positive Damping in Structures
Source: Nagarajaiah et. al. (2010)
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Pseudo-Negative Stiffness in BridgesSource: Iemura and Pradono (2003)
Cyclic Testing of PNS Damper
With PNS,Both Force and Displ.Reduced
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True Negative Stiffness Device
Deformed ShapeUndeformed Shape
- Device is completely passive (no external power source needed)- Device has adaptive behavior (stiffness varies with displacement
in a controllable manner)
Passive AdaptiveNSD
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Analytical Force-Displacement
Relation of NSD
Distance from spring pin to hinge pin L1 = 10 in
Distance from lever pin to hinge pin L2 = 5 in
Vertical length of main spring Lp = 30 in
Stiffness of main spring Ks = 0.8 kips/in
Pre-load of main spring Pin = 4.4 kips
Fg = Force in gap-spring assembly
Values of Parameters for Bridge Model Analysis
Neglecting inertial effects, friction at pins, and flexibility of steel framing members:
11 2
2 22 1 2
2in s p pNSD s g
s
P K L L LL LF K u F
L L L L u
vAB
vBC
vCDls
l1
l2
uU( )l1
l2
FBh
FNSD
FS
FS
A
B
C
DFg
FBv
FDv
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Force-Displacement Relation in Gap-Spring Assembly
1
1 21
1 2
s gap
g s ss gap gap gap
s s
k u u d
F k kk d u d u d
k k
Disp.
Forc
e
dgap
Pcomp
Kstiff
Kstiff Ksoft
Kstiff +Ksoft
Pcomp
KSoft KStiff
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NSD Force-Displacement Relation
Source: Sarlis, Pasala, Constantinou, Reinhorn, Nagarajaiah, and Taylor (2011)
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Implementing NSD's in Bridge Model
• Quarter-scale single-span highway bridge with clear span of 4.8 m and deck weight of 35.5 kips
• NSD's located under bridge deck within isolation system• Isolation system:
Component- and System-Level Analytical Force-Displacement Relations
Bearings
Bridge with
Bearings + NSD'sBearings +
NSD's
NSD's
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Cyclic Testing of NSDs
Harmonic TestAmplitude = 3"Freq. = 0.01 Hz
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Shake Table Testing of Bridge Model with NSDs Installed
SolidWorks Model
SAP2000 Model
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Building and Preparing
Bridge Model
New Bridge Deck
Torsional Restraint and NSD Force Transfer ColumnExisting Bridge Pier
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Building and Preparing Bridge Model (Cont.)
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Quarter-Scale Bridge Model on Shake Table at NEES-UB
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Sine Sweep Test of Bridge Model with NSDs
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Seismic Test of Bridge Model with NSDs: Kobe Earthquake (KJM000 – 100%)
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Summary
• Conceptual Development– Concept of weakening and damping (via negative stiffness and positive
damping) offers potential for improved seismic performance by reducing both forces and displacements.
• Validation of Analytical Model via Cyclic Testing– Mechanical negative stiffness device (NSD) has been developed and cyclic tests
have been performed. Simplified analytical model captures cyclic response.
• Shake Table Testing of Bridge Model– Negative stiffness device has been implemented in a scale-model bridge
structure. Numerical simulations demonstrate potential for improved seismic performance. Shake table testing is underway.
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Acknowledgments• National Science Foundation (NSF) under Grant No. CMMI- 0830391
• Mr. John Metzger (Engineering Manager), Taylor Devices, Inc.
• Mr. Peter Fasolino, K&E Fabricating Co.
• Staff of NEES & SEESL Laboratories at University at Buffalo (listed alphabetically)– Thomas Albrechcinski (Site Operations Manager)– Myrto Anagnostopoulou, M.Sc. (Structural and Test Engineer)– Christopher Budden (Electronic/Instrumentation Specialist)– Jeffrey Cizdziel (Mechanical Technician)– Goran Josipovic (IT Service Manager)– Duane Kozlowski (Lead Mechanical Technician)– Lou Moretta (Mechanical Technician)– Mark Pitman (Technical Services Manager)– Robert Staniszewski (Mechanical Technician)– Scot Weinreber (Electronic/Instrumentation Engineer)– Shomari White (IT Specialist)