Performance estimates in seismically isolated bridge structures
Download
1 / 23

Performance Estimates in Seismically Isolated Bridge Structures - PowerPoint PPT Presentation


  • 491 Views
  • Uploaded on

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

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Performance Estimates in Seismically Isolated Bridge Structures' - Sharon_Dale


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Performance estimates in seismically isolated bridge structures l.jpg
Performance Estimates in Seismically Isolated Bridge Structures

Gordon Warn

Young Researchers’ Symposium

Tokyo, Japan

June 2003


Personal information l.jpg
Personal information Structures

  • 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 l.jpg
Technical approach Structures

  • 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 l.jpg
Performance measures Structures

  • 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 l.jpg
Modeling seismic isolators Structures

  • 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 l.jpg
Displacement estimates Structures

  • 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 l.jpg
Displacement estimates Structures

  • 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 l.jpg
Displacement estimates Structures

  • Spectral demands for NF (Bin 1)

    • 5% critical damping


Displacement estimates12 l.jpg

Force Structures

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 l.jpg
Displacement estimates Structures

  • Bidirectional excitation

  • Unidirectional excitation


Displacement estimates14 l.jpg
Displacement estimates Structures

  • 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 l.jpg
Displacement estimates Structures

  • Displacement multiplier

Bin 2M: LMSD


Energy dissipation demands l.jpg
Energy dissipation demands Structures

  • 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 l.jpg

Force Structures

Fmax

Fy

Kd

Qd

Ku

Displ.

dmax

dyield

EDC

Energy dissipated demands

Normalized Energy Dissipated (NED )


Slide18 l.jpg

NED for NF ground motions Structures

Bidirectional response-history analysis


Normalized energy dissipated l.jpg
Normalized energy dissipated Structures

Td =2.0 seconds


Energy dissipated demands20 l.jpg
Energy dissipated demands Structures

Rate-of-energy dissipated

Isolator properties:

Qd=0.06

Td =4.0 sec.

Ground motion component:

RIO360


Energy dissipated demands21 l.jpg

Force Structures

Keff

Kd

Qd

Displ.

dmax

Energy dissipated demands

Equivalent harmonic frequency

Results of URHA using ground motion record: RIO360


Conclusions l.jpg
Conclusions Structures

  • 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 l.jpg
Acknowledgements Structures

  • Professor Andrew Whittaker

  • Professor Kawashima

  • MCEER / FHWA

  • Natural Hazard Mitigation in Japan Program

  • National Science Foundation

  • Japan Society for the Promotion of Science