Hello Saurabh
The stress increase for occasional loads apply to loads that - as the name suggest - are occasional. Generally speaking, the weight of the vessel and its design contents are sustained loads.
Where seismic and wind loads are added to the sustained loads, it is permissible to use the higher stresses. However, our software takes the conservative approach, and does not use the occasional load factor when saddle supports are considered.
We do consider the occasional load factor in the design of towers, where the stresses can be increased (by the occasions load factor). This is particularly important, as thicknesses might otherwise be over sized.
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Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM