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CONTENTS• １．Damages of Past Earthquakes

Current Status of Seismic
Retrofitting Technology• ２．Seismic Diagnosis Method

Building Control Section
Urban Building Division
Bureau of Urban Development, TMG• ３．Seismic Retrofitting Method

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Damages by the Great Hanshin-Awaji Earthquake

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Damages by the Great Hanshin-Awaji Earthquake

・ Severe damages observed for the buildings constructed before 1981
・ Buildings after 1981 were not severely damaged, indicating basicallythe adequacy of the current earthquake resistance standards
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Damages by the Great Hanshin-Awaji Earthquake

Damages by the Great Hanshin-Awaji Earthquake

5Damages by the Great Hanshin-Awaji Earthquake

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Damages by the Niigata Chuetsu Earthquake

・ The quake caused many ground failure and landslide
・ Long rain before the quake softened the ground・ Buried houses and road by landslide （Yamakoshi village 2004.10.29）
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Sesmic Retrofitting Technology

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Damages by the Niigata Chuetsu Earthquake

The column failed to support thevertical load due to the large
horizontal deformation as theresult of the cross cracks causedby shear force
910

There were big
shear cracks on thewall and theopposite side canbe seen through.
Columns
considerably
distorted
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Sesmic Retrofitting Technology

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Seismic Diagnosis （for RC structures）(Judgment on whether or not a building satisfies the required seismic
performance against the possible large earthquakes)

13First Order Diagnosis

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Second Order Diagnosis• The most simple method• The most common method• Suitable for buildings with sufficient shear walls• Suitable for the buildings whose vertical members(column and shear wall) are likely to collapse before
horizontal members (beam) collapse• Determining the seismic performance from thehorizontal section area of shear walls and columns aswell as the strength of concrete

15Sesmic Retrofitting Technology• Determining the seismic performance with theultimate strength of vertical members, such ascolumns and shear walls

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Third Order (Precise) diagnosis

The Result of Seismic Diagnosis• Suitable for the buildings whose horizontal members(beam) are likely to collapse before vertical members(column and shear wall) collapseIndex• Is = Index of seismic performance• Determine the seismic performance with thestrength of columns, shear walls as well as beams

WhenIs ≧ 0.6• Frame analysis and advanced knowledge andjudgment skill are necessary

the risk of collapse is considered low

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The Process of Seismic Diagnosis/Retrofitting

PreparationStart¾ visual inspection

Preliminary survey¾ Age of the building(standards applied)¾ Building record

Investigation and calculation on the strengthand ductility of the building
first/ second/ third order diagnosis
Improvement notneededImprovement needed
Basic design of retrofitting
Approximate expenses

Structural drawings &structural calculation sheets

Basic consideration on diagnosis

Decide the level of seismic
performance of the building

Decision of thediagnosis levelwith building
owner

Not retrofit

Retrofit
Detailed design of retrofitting

On-site survey
Continuoususe
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Sesmic Retrofitting Technology

Demolish& rebuild

As it is

Detailed expense &construction Process

Construction

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Seismic retrofitting methods (examples)

1. Reduce the weight of building

Seismic Retrofitting Methods• Reduce the weight of building• Add new structural members to scale up theseismic performance

One floor was removed from anold school building in 2008 toenhance its seismic performance(The capacity of three-story isenough for the school due to lowbirthrate)• Strengthen the existing structural members
to increase their strength and ductility• Reduce the seismic force inputted to thebuilding

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Seismic retrofitting methods (examples)

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Seismic retrofitting methods (examples)

2. Add new structural members to scale up
the seismic performance

2. Add new structural members to scale up
the seismic performance

New shear wall
was constructed
Braces were added to thebuilding to elevate theearthquake performance

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Sesmic Retrofitting Technology

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Seismic retrofitting methods (examples)

Seismic retrofitting methods (examples)

3. Strengthen the existing structural members
to increase their strength and ductility

3. Strengthen the existing structural members
to increase their strength and ductility

Wrapping carbon
fiber sheets aroundreinforced concrete
columns
Wrapping carbon fiber sheets aroundreinforced concrete columns
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Seismic retrofitting methods (examples)

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Seismic retrofitting methods (examples)

3. Strengthen the existing structural members
to increase their strength and ductility

4. Reduce the seismic force inputted tothe building

Separation of columns
from low walls

Installation of seismic isolation
devices in the foundation

seismicisolation
devices

Without separation, seismic force
concentrates at one point andcause rupture27

Sesmic Retrofitting Technology

Construction
is conducted
only forfoundation

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Seismic retrofitting methods (examples)

Seismic retrofitting methods (examples)

4. Reduce the seismic force inputted tothe building
Installation ofseismic isolationdevices in thecolumns at theintermediate floor

Large shear force

Small shear force

seismic isolation floor

Building withseismic isolation

Building withseismic isolation

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Seismic retrofitting methods (examples)

Remove existingcolumns

Seismic isolation device

Take off the temporary
backup columns

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4. Reduce the seismic force inputted tothe building

Set-up of vibration control brace toabsorb earthquake energy

Seismic isolation device

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Sesmic Retrofitting Technology

Install temporary
backup columns

Seismic retrofitting methods (examples)

4. Reduce the seismic force inputted tothe building

Seismic isolation device withfireproof covering

4. Reduce the seismic force inputted tothe building

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Seismic retrofitting methods (examples)

Seismic retrofitting methods (examples)

4. Reduce the seismic force inputted tothe building

4. Reduce the seismic force inputted tothe building

Floor plan

A terminal building with two underground lines and one ground line
Higher floors for department store
Complex building used by general public
We will see it tomorrow
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Sesmic Retrofitting Technology

Elevation plan

The red lines show the placesof vibration control brace

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