Okuma Memorial Hall Base Isolation Retrofit

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Okuma Memorial HallBase Isolation Retrofit

• Taft Tucker
• Rice University

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Waseda University

• Founded in 1882 by samurai scholar Okuma
  Shigenobu
• One of oldest and most prestigious universities
  in Japan
• About 45,000 undergrads including almost 7,000
  Science and Engineering students

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Okuma Hall

• shortly after Okumas death in 1922 construction
  began
• Construction delayed by Great Kanto Earthquake
• Construction Completed in 1927

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Base-Isolation Retrofit

• Would reduce superstructure damage in the event
  of earthquake
• However, very expensive to retrofit

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Static Analysis

• FEM Model
• Subjected to Japans standard lateral earthquake
  loading (Ai Coefficient)

194.5 kN
194.5 kN
194.5 kN
40.5 kN
51 kN
51 kN
123.5 kN
123.5 kN
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Derivation of Lateral Stiffness

• Used nodal displacements to calculate inter-story
  drift and derive lateral stiffness to be used in
  dynamic analysis

0.283 in.
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Earthquake Analysis Fixed Base Case

• Natural period and damping of building was found
  by solving eigenvalue problem. T .62 sec.
• Subjected building to scaled El Centro earthquake
  with max ground acceleration 150 cm/sec2
• Used Linear Acceleration Method to return top
  story deflection, velocity, and acceleration and
  base shear time-history plots.

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Dynamic Analysis Results Base Shear
1183 kN

• Max Base Shear 1183 kN

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Dynamic Analysis Results Shear Coefficients

• First Level 0.30 Second 0.42 Third 0.45
  Fourth 0.47

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Dynamic Analysis Results Deflection
4.22 cm

• Max Deflection 4.22 cm

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Dynamic Analysis Results Velocity
41.6 cm/s

• Max Velocity 41.6 cm/s

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Dynamic Analysis Results Acceleration
5.47 m/sec2

• Max Acceleration 5.47 m/sec2

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Base Isolation Model

• Used multiple degree of freedom model for base
  isolation analysis with base stiffness set to
  give a period of 3 seconds.
• Passive Analysis
• Yield Load Set to 1 of building weight
• Compared with Uncontrolled Case
• Damper Yield Load set to zero
• Scaled El Centro
• 150 cm/sec2 for comparison with fixed base case

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Passive Control w/ Friction

• Magnetorheological Damper used at isolation level
• Yield load is static value throughout excitation,
  passive control
• Behavior is similar to passive friction damper

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Passive Results Top Story Acceleration

• Max Acceleration 0.57 m/sec2
• reduction of 90 compared to fixed base case

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Passive Results Base Deflection

• Max Base Displacement 5.1 cm
• Decreased from 18.5 cm (72) in No Friction
  Damping Case

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Passive Results by Story

• Acceleration Deflection
• Max 0.57 m/sec2 Max
  5.1 cm

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Passive Results Base Shear

• Max Base Shear 231 kN
• 80 reduction from fixed base case

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Damper Forces
Yield Force
Yield Force 1 of Building Weight
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Is passive good for stronger EQ?
-- El Centro -- Taft -?- Hachinohe

• As Earthquake acceleration increases,
  effectiveness at reducing deflection decreases.

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Semi-Active Control

• Used MR damper to vary level of damping on base
  of building by changing the yield load of Damper
• Yield Load varied by changing electric current
  supplied to damper

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Semi-Active Control Strategy

• Yield Load a x Mass x Absolute Acceleration
• Performed Optimal Alpha Analysis to Decide which
  alpha would best reduce both Acceleration and
  Deflection
• Used Scaled Hachinohe, Taft, and El Centro
  Earthquakes
• Max Acceleration 500 cm/sec2

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Semi-Active Control Strategy

• Yield Load a x Mass x Absolute Acceleration

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Optimal Alpha Analysis Acceleration
0.3
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Optimal Alpha Analysis Deflection
0.3
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Semi-Active Control Results Top Story
Acceleration

• Max Acceleration .59 m/sec2
• Roughly equivalent to passive damping

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Semi-Active Control Results Base Deflection

• Max Deflection 7.5 cm
• Increase of 2.4 cm from Passive Control

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Semi-Active Control Results by Story
Deflection
Acceleration
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Semi-Active Control Results Base Shear

• Max Shear 405 kN
• Increase from passive case

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Base Shear - Active vs. Passive
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Semi-Active Control Results Damper Forces
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How does Semi-Active Control Perform in
Larger Earthquakes?
Percentage of Uncontrolled Deflection
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Conclusions

• Base Isolation would reduce forces in Okuma Hall
  during EQ, however displacement is increased
  considerably.
• Passive control reduces displacement for small
  EQ, but does not perform well under larger EQ.
• Semi-Active Control should be used to control
  deflection in event of large EQ.