Use of Advanced Technologies for Seismic Hazard Mitigation

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Use of Advanced Technologies for Seismic Hazard
Mitigation

• Keri L. Ryan
• Assistant Professor
• Civil and Environmental Engineering
• Utah State University

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To meet minimum code standards, civil engineering
structures are designed for life safety in an
earthquake.
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Many devices are available to protect structures
from earthquakes.
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Seismic isolation and damping can reduce force
and displacement demands so structure remains
elastic or damage free
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Seismic isolation reduces the forces transferred
to a structure by lengthening its natural period
Displacement
Period
k1,m1
k2,m2
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Lead rubber bearings provide lateral flexibility
and weight carrying capacity with alternating
layers of rubber and steel
Bilinear model
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Friction pendulum system allows the structure to
slide on a curved friction surface.
Bilinear model
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Viscous or friction dampers dissipate energy to
reduce structural response.
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Smart dampers use feedback control to adjust
the amount of damping in real time.

• MR (magneto-rheological) damper uses a fluid that
  changes viscosity in the presence of a magnetic
  field.
• Control algorithms decide what magnetic field to
  apply.

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Worldwide Scenario

• United States
• 80 isolated buildings and 60 buildings using
  dampers
• Retrofit of landmark historic buildings
• New design of emergency response facilities and
  supercomputing centers

• Worldwide
• gt 2000 isolated buildings in Japan
• Several hundred applications in China and Taiwan
• Widespread commercial and residential use

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Obstacles to Use of Seismic Isolation in the
United States

• Cost of devices and accessories
• Inability to convey benefits to building owners
• Complex and inconsistent design code
• Strict performance goals
• Extensive testing and peer review
• Typical design office inexperienced and does not
  try to sell technology

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NEES TIPS Project (NSF Award No. CMMI-0724208)
Tools to Facilitate Widespread Use of Isolation
and Protective Systems

• 4 year, 1.5 million, multi-institutional grant
• Shaking table and hybrid testing at SUNY Buffalo
  and UC Berkeley
• Full scale tests on worlds largest shake table,
  E-Defense, in Japan

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NEES TIPS Project (NSF Award No. CMMI-0724208)
Tools to Facilitate Widespread Use of Isolation
and Protective Systems

• 4 year, 1.5 million, multi-institutional grant
• Shaking table and hybrid testing at SUNY Buffalo
  and UC Berkeley
• Full scale tests on worlds largest shake table,
  E-Defense, in Japan

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¼ scale test at UC Berkeley
Full scale test at E-Defense, Japan
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TIPS Project Objectives

• Fill knowledge gaps regarding modeling and
  performance
• Component characterization tests
• Isolator and damper modeling
• Performance limit states
• Full scale testing
• Worldwide information database

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Isolator behavior is complex and rate/scale
dependent.
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TIPS Project Objectives

• Fill knowledge gaps regarding modeling and
  performance
• Component characterization tests
• Isolator and damper modeling
• Performance limit states
• Full scale testing
• Worldwide information database

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TIPS Project Objectives

• Reduce cost of using seismic isolation
• Component sensitivity study
• Configuration and detailing issues
• Improved static design procedure for regular
  buildings
• Tools to meet performance goals
• High performance system tests
• Extend performance-based analysis tools to
  isolated buildings
• Needs assessment and professional participation

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Strategies for cost reduction

• Move isolation plane

• Architectural detailing, electrical, plumbing to
  accommodate displacements

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Strategies for cost reduction

• Simplified Design
• Isolator deformation
• Distribution of static forces
• Sensitivity study of devices to reduce need for
  testing

• Allow moderate yielding

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TIPS Project Objectives

• Reduce cost of using seismic isolation
• Component sensitivity study
• Configuration and detailing issues
• Improved static design procedure for regular
  buildings
• Tools to meet performance goals
• High performance system tests
• Extend performance-based analysis tools to
  isolated buildings
• Needs assessment and professional participation

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Long term vision

• Vulnerability of isolated buildings to long
  period, high velocity pulses from very rare
  motions remains an issue.
• Smart structures and smart isolation systems that
  can tune their frequencies in real time.

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Applications of Fractional Calculus

• Fractional Control Algorithms
• Applied to fast hybrid testing of MR dampers
  (Abdollah Shafieezadeh)
• Fractional Modeling of Seismic Isolation Bearings

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Modeling issues

• Amplitude dependence
• Frequency dependence
• Strain hardening of high damping rubber
• Cyclic degradation (recoverable and
  non-recoverable)

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• Currently
• Complex models up to 10 parameters to be fitted
• Everyone uses bilinear models
• Vision
• Simpler models using fractional calculus
• Determine and capture essential effects
• Provide tools to fit models using database test
  data