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RE: Increases in Foundation Bearing Pressure For Wind and Seismic Loading

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Usually the project geotechnical engineer will use a factor of safety of 3-4
in order to provide the structural engineer with a usable allowable bearing
pressure.  The intent of seismic design is to protect life safety which, in
an ideal world, means that the building does not fall down (nor do bits fall
off) in the event of a major earthquake.  That does not preclude the
building from being permanently unusable after an earthquake.  It would seem
reasonable to allow the structural engineer the use of a slightly higher
allowable bearing pressure for transient loads, i.e. there is an acceptable
increase in differential settlement (or local yielding of the soil structure
in the worst case). A 33% increase in ASBP would still leave a suitable
factor of safety.
 
While the above does not reference any specific printed theory, I would
expect Idriss and/or Seed or Das to have some theoretical discussion of the
above.