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

(NEESR - Network for Earthquake Engineering Simulation Research) Project Team NEESR-SG: Development of Next Generation Adaptive Seismic Protection Systems Satish Nagarajaiah Professor Civil & Mechanical Eng. Rice University Michael Symans Associate Professor Civil Engineering Rensselaer Polytechnic Institute Andrei Reinhorn University at Buffalo Michael Constantinou Jian Zhang Assistant Professor Univ. of Calif. Los Angeles Douglas Taylor President, Taylor Devices, Inc. Mechanical Engineering Taylor Device Inc. Research supported by National Science Foundation CMMI Grant No. 0830391 (NEESR - Network for Earthquake Engineering Simulation Research)

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

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

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

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

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

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

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

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

Force-Displacement Relation in Gap-Spring Assembly dgap Pcomp Kstiff Kstiff Ksoft Kstiff +Ksoft Pcomp KSoft KStiff

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

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

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

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

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

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

Building and Preparing Bridge Model (Cont.)

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

Sine Sweep Test of Bridge Model with NSDs

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

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.

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)