Transcript Nagarajaiah et. al. (2010) Pseudo
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 Civil & Mechanical Eng.
Professor Michael Symans Associate Professor Andrei Reinhorn Professor Michael Constantinou Professor Rice University Civil Engineering Rensselaer Polytechnic Institute Civil Engineering University at Buffalo Civil Engineering University at Buffalo Jian Zhang Assistant Professor Douglas Taylor President, Taylor Devices, Inc.
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
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Seismic Protection Systems for Bridges
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Concept of Negative Stiffness
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Development of Mechanical Negative Stiffness Device
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Implementation of Negative Stiffness Device within a Quarter-Scale Bridge Structure
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Advanced Seismic Protection Systems for Bridges
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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 4
Improved Seismic Performance via Combined Weakening and Damping
Source: Reinhorn et. al. (2002) 5
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) 7
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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F Bh l 1 C F S l 2 B F Bv A F NSD v AB v BC l s U( ) 2 u F S D F g F Dv v CD
Analytical Force Displacement Relation of NSD
Neglecting inertial effects, friction at pins, and flexibility of steel framing members:
F NSD
P in
L s p
K s
L L
1 2 2
L
2
L
1
L p
L
1
L
2 2
u
2
g F g = Force in gap-spring assembly
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 L 1 = 10 in L 2 = 5 in L p = 30 in K s = 0.8 kips/in P in = 4.4 kips 10
Force-Displacement Relation in Gap-Spring Assembly d gap K stiff K soft K stiff +K soft P comp K Soft K Stiff
F g
k d s
1
gap
k u s
1
k k k s
1
s
2
s
1
k s
2
gap
gap
gap
K stiff Disp.
P comp
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NSD Force-Displacement Relation
Source: Sarlis, Pasala, Constantinou, Reinhorn, Nagarajaiah, and Taylor (2011) 12
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 13
Component- and System-Level Analytical Force-Displacement Relations
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Cyclic Testing of NSDs Harmonic Test
Amplitude = 3" Freq. = 0.01 Hz 15
Shake Table Testing of Bridge Model with NSDs Installed
SAP2000 Model SolidWorks Model 16
Building and Preparing Bridge Model
New Bridge Deck Existing Bridge Pier
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
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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.
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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.
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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) 24