Mitigation

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Mitigation
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Structural Preventions

• Earthquakes are a natural phenomena and cannot be
  predicted accurately.
• Due to its unpredictability it is difficult to
  prepare for it hence it causes widespread
  destruction.
• However there are ways to prevent its devastating
  affects.
• This PowerPoint will follow some earthquake
  mitigations

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Base-Isolation

• Weak buildings are most vulnerable to earthquake
  damage.
• This damage can be greatly reduced by Vibration
  isolation bearings. These bearings dampen
  earthquake ground movements before they reach the
  building.
• Also it allows the buildings move as one, this
  stops the building cracking.

Effectiveness Very effective when properly
installed.
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Cross Bracing

• Full-height, steel cross bracing can increase a
  buildings capacity to withstand seismic forces.
  Cross bracing can be on be on the inside or
  outside and is secured to the building at floor
  level. 

• Effectiveness
• Somewhat to very effective, depending on
  pre-disaster building condition and the extent of
  cross bracing.
• Limitations
• Foundation must be able to support bracing. 
• Multi-story cross bracing is less effective than
  cross bracing at each floor level

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• Cross bracing hold floors together and prevents
  the floors and walls collapsing. limit the
  movement of walls and absorb energy Usually to
  implicated to steel frame buildings.

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Shear Walls

• shear walls limit stresses in walls and absorb
  force. In some cases, an existing interior wall
  can be modified to act as a shear wall or be used
  as a form for a semi-shear wall which is still
  effective. 

• Effectiveness
• Very effective for increasing earthquake
  resistance and reducing damage.
• Limitations
• A new shear wall should be supported on a new
  reinforced concrete footing.

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Shear Stress
WALLS
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Brace or Support Chimneys

• Brick chimneys are heavy, brittle, and can fail
  unless reinforced near the top and supported by
  the building roof and walls. Chimneys on older
  buildings frequently suffer damage or collapse
  during earthquakes. Methods to mitigate damage
  are 
• Chimney secured with steel straps anchored to the
  roof with steel angle braces. 
• The chimney pipe enclosure can be reinforced
  using vertical and horizontal bars.
• For multi-storied buildings, chimneys can be
  anchored at each floor level using steel wrap
  ties.

• Limitations
• For large, complex chimneys, all elements should
  be checked to ensure mitigation will not
  exacerbate damage.
• May not be cost-effective for small, simple
  chimneys.

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Minor Changes

• Rigid Wall Panels
• During an earthquake, rigid wall panels
  attached to the outside of buildings can be
  damaged due to inflexibility in the connections
  to the frame. Connections can be modified to
  allow make it flexible enough to withstand
  earthquake forces.
• This is useful as this panels could fall of and
  hurt people.
• Effectiveness
• Somewhat to very effective depending on the
  existing building condition.

Replace old weak bricks with breeze blocks or new
more larger solid materials.
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• Windows shatter during an earthquake. It is huge
  problem as it may fall on people and be extremely
  dangerous. There two ways to reinforce them
• Stronger frames, this way the glass is less
  likely to move out of shape and shatter. As its
  more firm and less room for the glass to move and
  shatter.
• During an earthquake, window frames can
  experience extreme shaking or distortions that
  trigger glass breakage. Tempered glass is
  stronger than conventional glass and breaks into
  smaller, less dangerous fragments.
  Wire-reinforced glass, or adhesive film applied
  to existing windows, can hold the glass fragments
  together, reducing damage and falling hazards.

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MEDC Govt Mitigation

• As you cannot predict an earthquake the most you
  can do is being as preapred as possible. The govt
  does this by
• Drills this could be in workplaces or in
  schools. This make people more aware to
  earthquake and their destruction. So carry out
  drills they will know what to do in an event of
  an earthquake.
• Hazard Mapping With information from pervious
  earthquakes and geological studies you can map
  danger spots. This enables emergency services to
  plan routes to get these areas if anything
  happens.
• Protection to important buildings such as
  hospitals, they are given priority such as
  emergency power and immediate help to get up and
  running after an earthquake
• Prepare emergency workers for many people the
  event of an earthquake can be over-whelming. So
  preparing them in hope to cop and advice other
  people during these conditions are very
  important.
• Building Restrictions Certain buildings have to
  gain special permissions to prove they are
  earthquake resistant and safe.

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LEDC Govt Mitigation

• The pervious mitigation measures apply mainly to
  MEDCs.
• The sad truth is most LEDC do have some measures
  in place but due to high levels of corruption
  these measures are overlooked. It is only after
  the earthquake it is evident the extent of the
  damage and how corruption is a silent killer.
• Also many LEDC hot spots for earthquake maybe on
  built up urban areas which attracts people for
  jobs. The huge influx of people put a lot of
  pressure on buildings and the housing is cheap
  and weak, therefore the toll of damage and
  injuries increase.
• Also many LEDC cannot afford the expensive
  structural mitigation.