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Plate movement

Plate movement.

micheal
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Plate movement

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  1. Plate movement

  2. Earthquake = sudden release of energy in the Earth’s crust that creates seismic waves. They are measured by the Richter Scale, which is an exponential scale. Magnitude 3 and below are very weak and barely felt, magnitude 7 and above cause serious damage over large areas. The damage and severity of shaking depends on the earthquake’s depth.

  3. Surface waves travel along the surface of the Earth after P waves and S waves.

  4. Earthquake Engineering The purpose is to mitigate earthquake hazards. This is done through: Preventingnon-structural damage in frequent minor ground shaking Preventingstructural damage and minimizingnon-structural damage in occasional moderate ground shaking Avoidingcollapse or serious damage in rare major ground shaking

  5. Earthquake Engineering • Damage to structures may result from different seismic effects. • Ground failure (surface faulting and vibration of soil) • Vibrations transmitted from the ground to the structure. • Structural engineers are most concerned with the vibration of the structure in response to ground shaking at it’s foundation.

  6. Seismic Structures • 2012 EERI Seismic Design Competition - Stanford University – YouTube • UTAustin - Seismic Design Competition 2011 – YouTube • JohnsHopkins - Seismic Design Competition 2011 – YouTube • UCLA - Seismic Design Competition 2011 - YouTube

  7. Seismic Effects – Ground Failure • Soil instability during earthquakes can cause significant damage. Soil response depends on the characteristics of the soil layers, depth of the water table, and intensity/duration of ground shaking. • Liquefaction is when unconsolidated soil acts like a liquid. This can undermine the foundations of structures, causing very serious damage. Ex: Haiti

  8. Seismic Effects – Ground Failure • Liquefaction works when earthquake waves cause water pressures in increase in the sediment, which causes the sand grains to lose contact with each other.

  9. Seismic Effects – Ground Failure • Typical effects of liquefaction include: • Loss of bearing strength – soil cannot support structures • Lateral spreading of soil – ground slides down gentle slopes or structures move around on a buried liquefied layer • Ground oscillation – the surface layer, riding on a buried liquefied layer, is thrown back and forth by the shaking. • Settlement – when liquefied ground re-consolidates after the earthquake, the ground surface may settle or subside as the liquefied soil becomes more dense.

  10. Seismic Effects – Ground Vibration • The seismic performance (degree of damage) of a structure depends on: • type of foundation • configuration of the structure • structural material • design and construction details

  11. Seismic Effects – Ground Vibration • The main points to remember are that the whole structure-foundation system should work as a unit, and that the superstructure be tied or anchored properly to the foundation.

  12. Design Proposal • Some items to research for your design proposal are: • Base isolation systems • Shear wall system • Building elevation control • Friction pendulum bearing

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