Buildings that Resist Earthquakes Better

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Buildings that Resist Earthquakes Better

• Ms. Michelle Beach, Midpark High School
• Mr. Jaz Dhillon, Withrow University High School
• Dr. Nathalie Mukolobwiez, Saint Ursula Academy
• Dr. Anant Kukreti (PI)
• Dr. Kelly Cohen (PI)
• Mr. Ravi Chalasani (GA)

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Buildings that resist Earthquakes better- Outline

• Background
• Research Goals
• Research and Data
• Experiment 1 Stiffness Test
• Experiment 2 Resonance
• Base Isolator
• Experiment 3 Free Vibration Test
• Viscous Damper effects
• Experiment 4 Active Mass Damper
• Conclusions Recommendations

Picture of the collapse of the Hanshin Expressway
in Kobe, Japan in 1995 The economic loss in the
earthquake was over 200 billion dollars.
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Background

• Earthquakes generate seismic waves which are
  filtered to a predominant frequency
• Buildings have natural frequency and damping
  coefficient
• Buildings behave as a set of masses and springs
• Frequency is a function of stiffness (spring) and
  mass

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Background cont.

• The Problem is Resonance
• When natural frequency of building matches
  Earthquakes frequency.

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Research Goals
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Research and Data

• Buildings that Resist Earthquakes Better

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Experiment 1Stiffness Test

• Force applied by Load Sensor
• Resulting displacement recorded by LVDT

Displacement
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Experiment 1Stiffness Results
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Experiment2Resonance

• Shake Table
• Varying frequencies
• Two LVDT
• Measures displacement of
• Shake Table
• Model
• Base Isolators
• 2 sizes

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Resonance Results

• Transmissibility (TR)
• Ratio of the total acceleration of the structural
  mass to the peak ground acceleration. The figure
  plots TR against frequency ratio ?/?n where ?n is
  the natural frequency. The left shift of the
  maxima shows how strong is the effects of Base
  Isolators (BI) on the model (M3.52 kg, L1 15.9
  cm)

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Experiment 3Free Vibration Test

• Only an initial force is applied (displace and
  release w/ electromagnet).
• Lateral oscillation recorded to determine natural
  frequency.

LVDT
Actuator
Electromagnet
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Free Vibration Results

• Theoretical vs Experimental

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Free Vibration Damping

• In free vibration, the structure eventually stops
  oscillating.
• It has a natural damping component, called the
  damping coefficient, c.
• The damping coefficient can be derived
  experimentally through observing the decrease in
  amplitude during free vibration.

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Damping Data

• Natural damping with free vibration
• c 2mp

(28.3 cm)
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Damping Results 1

• Damping Coefficient versus Length

• Damping Coefficient versus Mass

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Experiment 3Viscous Damper

• Study effects of viscous damper on the damping
  rate

• Free Vibration Test
• Viscous Damper
• Canola oil
• Glycerin

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Damping Results 2
With viscous damper of different viscosities
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Experiment 4 Active Mass Damper

• Results
• Active Mass Damper ON
• Increased damping rate

AMD cart
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Conclusions

• Mass-Spring Model representation of building
• Valid
• Stiffness
• Decreases as length of column increases
• Natural Frequency
• Decreases as
• Mass of floor increases
• Length of column increases

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Conclusions cont.

• Base Isolators BI
• Lower the stiffness
• Lower the natural frequency
• The smaller the BI the greater the shift
• Viscous Dampers
• Increase the damping rate
• The higher the viscosity the greater the damping
  
• Active Mass Damper
• Increase the damping rate
• More efficient than viscous dampers

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Recommendations

• Modify design of structure to incorporate
  leveling screws
• Investigate the use of Motion Detectors (Pasco)
  in lieu of LVDTs
• Test ADM on shake table

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Acknowledgements

• Dr. Anant Kukreti (PI), Professor Associate
  Dean for Engineering Education Structural
  Engineering, University of Cincinnati
• Dr. Kelly Cohen (PI), Associate Professor of
  Aerospace Engineering Engineering Mechanics,
  University of Cincinnati
• Mr. Ravi Chalasani, PhD Student of Civil and
  Environmental Engineering, University of
  Cincinnati
• Ms. Chelsea Sabo, Graduate Assistant of Aerospace
  Engineering Engineering Mechanics, University
  of Cincinnati
• Dr. Richard Gass, Assistant Professor of Physics,
  University of Cincinnati
• Mr. W. Henry Leach, Technical Professional of
  Physics, University of Cincinnati
• RET Teachers Site for Civil Infrastructure
  Renewal and Rehabilitation. National Science
  Foundation Grant ID EEC 0601960, Dept. of Civil
  and Environmental Engineering, University of
  Cincinnati.

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Questions?

• Thank you!