All,

In an offshore project, there are no "W" term in loadcase for FATIGUE. But the calculated FATIGUE value varies after removing insulation thickness and insulation density. How is it possible ?

Regards

Nonlinear effects would make this possible.

Thanks Mr.Dave Deihl

Can you please explain a bit in detail how Non-Linear effects can play a role like this ???

I am unable to figure-out exactly what you meant ?

Thanks and Regards,
Gow

You are providing very few details so I cannot respond to your specific situation.
Fatigue evaluation is working with change in load or change in stress as the pipe moves from one position or condition to the next. Added weight components may change the system response at, say, a +Y restraint. A large weight component may keep the pipe in contact with this restraint in both the operating and installed position while a lesser weight would allow the pipe to lift off the support in the operating state. This different response would cause different stress ranges.