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N. Attary and M.D. Symans Rensselaer Polytechnic Institute S. Nagarajaiah and D.T.R. Pasala

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

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N. Attary and M.D. Symans Rensselaer Polytechnic Institute S. Nagarajaiah and D.T.R. Pasala

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  1. 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

  2. Project Team Research supported by National Science Foundation CMMI Grant No. 0830391 (NEESR - Network for Earthquake Engineering Simulation Research)

  3. 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

  4. 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

  5. Improved Seismic Performance via Combined Weakening and Damping Source: Reinhorn et. al. (2002)

  6. Concept of Negative Stiffness Force develops in same direction as imposed force Adding Positive/Negative Stiffness to a Basic System with Positive Stiffness Positive vs. Negative Stiffness

  7. Working Principle of Negative Stiffness and Positive Damping in Structures Source: Nagarajaiah et. al. (2010)

  8. Pseudo-Negative Stiffness in BridgesSource: Iemura and Pradono (2003) Cyclic Testing of PNS Damper With PNS, Both Force and Displ. Reduced

  9. 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

  10. Analytical Force-Displacement Relation of NSD Neglecting inertial effects, friction at pins, and flexibility of steel framing members: FNSD A l2 vAB FBh B l1 FBv vBC C Fg= Force in gap-spring assembly FS Values of Parameters for Bridge Model Analysis u vCD l1 U( ) ls l2 FS D Fg FDv

  11. Force-Displacement Relation in Gap-Spring Assembly KstiffKsoft Kstiff +Ksoft dgap Force Pcomp Kstiff Pcomp Disp. KStiff KSoft

  12. NSD Force-Displacement Relation Source: Sarlis, Pasala, Constantinou, Reinhorn, Nagarajaiah, and Taylor (2011)

  13. 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

  14. Component- and System-Level Analytical Force-Displacement Relations • Bearings • Bearings + NSD's • Bridge with Bearings + NSD's • NSD's

  15. Cyclic Testing of NSDs Harmonic Test Amplitude = 3" Freq. = 0.01 Hz

  16. Shake Table Testing of Bridge Model with NSDs Installed SolidWorks Model SAP2000 Model

  17. Building and Preparing Bridge Model New Bridge Deck Existing Bridge Pier Torsional Restraint and NSD Force Transfer Column

  18. Building and Preparing Bridge Model (Cont.)

  19. Quarter-Scale Bridge Model on Shake Table at NEES-UB

  20. Sine Sweep Test of Bridge Model with NSDs

  21. Seismic Test of Bridge Model with NSDs: Kobe Earthquake (KJM000 – 100%)

  22. 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.

  23. 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) • MyrtoAnagnostopoulou, M.Sc. (Structural and Test Engineer) • Christopher Budden (Electronic/Instrumentation Specialist) • Jeffrey Cizdziel (Mechanical Technician) • GoranJosipovic (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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