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.
2012 Quake Summit, Boston, MA
Session 4, Base Isolation/Energy Dissipation
July 11, 2012
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Project Team
NEESR-SG: Development of Next Generation
Adaptive Seismic Protection Systems
Satish Nagarajaiah
Professor
Michael Symans
Associate Professor
Andrei Reinhorn
Professor
Michael Constantinou
Professor
Jian Zhang
Assistant Professor
Douglas Taylor
President, Taylor Devices, Inc.
Civil & Mechanical Eng.
Rice University
Civil Engineering
Rensselaer Polytechnic Institute
Civil Engineering
University at Buffalo
Civil Engineering
University at Buffalo
Civil Engineering
Univ. of Calif. Los Angeles
Mechanical Engineering
Taylor Device Inc.
Research supported by National Science Foundation CMMI Grant No. 0830391
(NEESR - Network for Earthquake Engineering Simulation Research)
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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 highway
bridge 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 Stiffness
Adding 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 Bridges
Source: Iemura and Pradono (2003)
Cyclic Testing
of PNS Damper
With PNS,
Both Force
and Displ.
Reduced
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True Negative Stiffness Device
Undeformed Shape
Deformed Shape
- Device is completely passive (no external power source needed)
- Device has adaptive behavior (stiffness varies with displacement
in a controllable manner)
Passive
Adaptive
NSD
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Analytical ForceDisplacement
Relation of NSD
Neglecting inertial effects, friction at pins, and
flexibility of steel framing members:
A
l2
FBh
l1
FNSD
vAB
B
FBv
vBC
F N SD
L p  L1
 Pin  K s L p
  L1  
L2

 
 Ks 
2


  L  
2
2
L
L
L2  u
s
1

 2 

u  F
g


C
Fg = Force in gap-spring assembly
FS
u
l
vCD
1
ls U( l2 )
FS
D
Fg
FDv
Values of Parameters for
Bridge Model Analysis
Distance from spring pin to hinge pin
Distance from lever pin to hinge pin
Vertical length of main spring
Stiffness of main spring
Pre-load of main spring
L1 = 10 in
L2 = 5 in
Lp = 30 in
Ks = 0.8 kips/in
Pin = 4.4 kips
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Force-Displacement Relation in
Gap-Spring Assembly
Force
dgap
Kstiff Ksoft
Kstiff +Ksoft
Pcomp
Kstiff
Pcomp
Disp.
KSoft
KStiff
k s 1u


Fg  
k k
k s 1 d gap  s 1 s 2 u  d gap

k s1  k s 2


u  d gap

u  d gap
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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:
– Elastomeric bearings (low damping)
– Elastomeric bearings + fluid viscous dampers
– Elastomeric bearings + NSD's
– Elastomeric bearings + fluid viscous dampers + NSD's
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Component- and System-Level
Analytical Force-Displacement Relations
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Cyclic Testing of NSDs
Harmonic Test
Amplitude = 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
Existing Bridge Pier
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Torsional Restraint and NSD Force Transfer Column
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)
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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)
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