Daman,

You should consider, as Dave Diehl has mentioned .... what allowable loads should apply to earthquake and design wind load ? And what are allowable load limits intended to protect ?

Earthquake is a survival situation and not an operational one. Surely the plant would shut down due to all manner of detectors in that event. Thus I would suggest, aim for stresses in piping below yield and leave it at that. Maybe the turbine vendor could help you out too. You should be aware that you can make the real situation of earthquake damage far worse by adding restraints and stiffening the pipe. Flexibility often means ability to survive.

So far as wind is concerned .... is the piping really exposed to direct wind at 180km/h ? It is common practice in refinery work to exclude piping less than 10m from the ground from wind loads, due to shielding of adjacent plant, unless it is an OSBL rack or similar. Worth a thought ?