Foundation, Concrete and Earthquake Engineering

Earthquake Requirements for Foundation and Sites

Foundation failures frequently lead to collapse or at least total economic loss of the building. Foundations should be concrete – traditional rock foundations may be used for single storeybuildings but they must be constructed to a high standard by experienced tradesmen.
For all foundations

1. Foundations should be designed to be stronger than the building elements above – we mustavoid foundation failures
2. If possible use one type of foundation throughout: e.g. piles or shallow footings• Individual foundations must be tied together in both directions
3. Ground beams should be at least as deep as columns
4. Consider settlement, especially differential settlement
5. Ensure all bearing pressures etc are similar
6. consolidation and liquefaction of the underlying soils.

Potentially Hazardous Buildings Sites

Buildings should not be constructed directly above steep slopes which are liable to become unstable, or below slopes which are susceptible to landslides and rockfalls.

Do not build too close to river banks: as a guide buildings should be at least 6 metres from a
riverbank in flood, and the floor should be at least 500mm above the flood level. For major rivers these figures are likely to increase.

Consider what happens to rain that lands on or near the building. How does it flow away from the building? Are new drains required? If so, where do the drains discharge?

Buildings must be founded in good ground. The foundations are arguably the most important
part of the building. A building on poor foundations cannot perform well in an earthquake.

The following things should keep in mind -

• The sub-grade must be sound with an allowable bearing pressure of at least 100 kPa

• Unstable ground should be avoided

• Poor soils result in a large increase in seismic forces

• The ground must be free from water at foundation level
• If surface water is present ensure suitable drainage is installed; the drain invert level must be
deeper than the foundation level

• Building should not be placed directly over fault-lines
• If a building must be constructed in a designated seismic hazard area it should be subject to
specific design.
• Site investigation is an essential part of every design

Soil types, changes in layers, depth to rock, depth of water table all effect actual loads
• Buildings must be connected to foundations (they must not be allowed to fall off

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