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Use of Advanced Technologies for Seismic Hazard Mitigation

Use of Advanced Technologies for Seismic Hazard Mitigation. Keri L. Ryan Assistant Professor Civil and Environmental Engineering Utah State University. To meet minimum code standards, civil engineering structures are designed for “life safety” in an earthquake.

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Use of Advanced Technologies for Seismic Hazard Mitigation

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  1. Use of Advanced Technologies for Seismic Hazard Mitigation Keri L. Ryan Assistant Professor Civil and Environmental Engineering Utah State University

  2. To meet minimum code standards, civil engineering structures are designed for “life safety” in an earthquake.

  3. Many devices are available to protect structures from earthquakes.

  4. Fixed - base structure Isolated Structure Seismic isolation and damping can reduce force and displacement demands so structure remains elastic or “damage free”

  5. Acceleration k1,m1 k2,m2 Seismic isolation reduces the forces transferred to a structure by lengthening its natural period Displacement Period k1,m1 k2,m2

  6. fb Q kb k1 ub Lead rubber bearings provide lateral flexibility and weight carrying capacity with alternating layers of rubber and steel Bilinear model

  7. fb Q kb k1 ub Friction pendulum system allows the structure to slide on a curved friction surface. Bilinear model

  8. Viscous or friction dampers dissipate energy to reduce structural response.

  9. “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.

  10. 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 > 2000 isolated buildings in Japan Several hundred applications in China and Taiwan Widespread commercial and residential use Worldwide Scenario

  11. 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

  12. 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 world’s largest shake table, E-Defense, in Japan

  13. 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 world’s largest shake table, E-Defense, in Japan

  14. ¼ scale test at UC Berkeley Full scale test at E-Defense, Japan

  15. 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

  16. Isolator behavior is complex and rate/scale dependent.

  17. 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

  18. 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

  19. Architectural detailing, electrical, plumbing to accommodate displacements Strategies for cost reduction • Move isolation plane

  20. Strategies for cost reduction • Allow moderate yielding • Simplified Design • Isolator deformation • Distribution of static forces • Sensitivity study of devices to reduce need for testing

  21. 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

  22. 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.

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

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

  25. fb Q kb k1 ub • 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

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