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Performance Estimates in Seismically Isolated Bridge Structures. Gordon Warn Young Researchers’ Symposium Tokyo, Japan June 2003. Personal information. Graduate research assistant Department of Civil, Structural, and Environmental Engineering Primary research interests

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performance estimates in seismically isolated bridge structures
Performance Estimates in Seismically Isolated Bridge Structures

Gordon Warn

Young Researchers’ Symposium

Tokyo, Japan

June 2003

personal information
Personal information
  • Graduate research assistant
    • Department of Civil, Structural, and Environmental Engineering
  • Primary research interests
    • Seismic Isolation, Passive Energy Dissipation Systems, Bridge Engineering
  • Academic advisor: Professor Andrew Whittaker
technical approach
Technical approach
  • Perform numerical simulation
    • Simple bridge model
    • Varied isolator parameters
  • Performance measures
    • Maximum isolator displacement
      • Review accuracy of static analysis procedure
      • Determine increase in displacement due to bidirectional seismic excitation
    • Energy demands
      • Develop prototype testing protocol
performance measures
Performance measures
  • Displacement estimate influences all aspects of analysis, design and construction
    • Superstructure and substructure forces
    • Design and full-scale testing of seismic isolators
      • Stability and strain demands for elastomeric bearings
      • Plan dimensions of sliding systems
  • Energy demand on seismic isolators
    • Design and full-scale testing of seismic isolators
    • Bearing acceptance criteria
modeling seismic isolators
Modeling seismic isolators
  • Lead-Rubber (LR) bearings
    • Coupled plasticity model
    • Bouc-Wen model
  • Friction Pendulum (FP) bearings
    • Coupled plasticity model
      • Account for variations in axial load
    • Bouc-Wen model
displacement estimates
Displacement estimates
  • Displacement estimate
    • Based upon work in the 1980s
    • Constant velocity region of the spectrum
    • Unidirectional response
  • Results of nonlinear response analysis
    • Benchmarked to static equation (buildings)
displacement estimates10
Displacement estimates
  • Bin description adapted from that developed by Krawinkler
  • Magnitude and distance-to-fault based on mainshock
  • Ground motions extracted from the PEER and SAC databases
displacement estimates11
Displacement estimates
  • Spectral demands for NF (Bin 1)
    • 5% critical damping
displacement estimates12

Force

Kd

Qd

Displ.

dmax

Displacement estimates
  • Response-history analysis
    • Unidirectional (URHA)
    • Bidirectional (BRHA)
  • Simple isolated bridge model
    • Rigid super- and substructures
  • Bilinear isolation systems considered
displacement estimates13
Displacement estimates
  • Bidirectional excitation
  • Unidirectional excitation
displacement estimates14
Displacement estimates
  • Update displacement equation
    • Option a:
  • Unidirectional displacement multiplier:
    • Based on results of URHA and BRHA
    • Orthogonal component
    • Coupled behavior of LR and FP bearings
displacement estimates15
Displacement estimates
  • Displacement multiplier

Bin 2M: LMSD

energy dissipation demands
Energy dissipation demands
  • Interpretation of isolator performance
  • AASHTO (Seismic Test)
    • 3 fully reversed cycles at 0.25dt,....1.25dt
    • 10 to 25 fully reversed cycles at 1.0d
    • 3 fully reversed cycles at dt
energy dissipated demands

Force

Fmax

Fy

Kd

Qd

Ku

Displ.

dmax

dyield

EDC

Energy dissipated demands

Normalized Energy Dissipated (NED )

slide18

NED for NF ground motions

Bidirectional response-history analysis

energy dissipated demands20
Energy dissipated demands

Rate-of-energy dissipated

Isolator properties:

Qd=0.06

Td =4.0 sec.

Ground motion component:

RIO360

energy dissipated demands21

Force

Keff

Kd

Qd

Displ.

dmax

Energy dissipated demands

Equivalent harmonic frequency

Results of URHA using ground motion record: RIO360

conclusions
Conclusions
  • Update displacement equation
    • Orthogonal component
    • Coupled behavior
    • Preliminary estimates of suggest 1.5-1.75
  • AASHTO testing protocols
    • Overly demanding (NED )
    • Performed statically (no specified frequency)
    • Replace with: 4 fully reversed cycles at T
acknowledgements
Acknowledgements
  • Professor Andrew Whittaker
  • Professor Kawashima
  • MCEER / FHWA
  • Natural Hazard Mitigation in Japan Program
  • National Science Foundation
  • Japan Society for the Promotion of Science
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