I am currently working on a piping system running through a pipe bridge linking two platforms. to be able to asses the fatigue, I calculated the cycle numbers and of course, I have applied the platform displacements on proper spots of the piping.
I would like to know which one of the following is the correct way of fatigue analysis for this situation:

1- making a (EXP) stress case and incorporate the stress reduction factor as per the code graph (fig. 302.3.5 in B31.3)

L1: W+P+T+D
L2: W+P
L3: L1-L2 (EXP) (modified stress reduction factor)

2- making a (FAT) case and using a proper fatigue curve

L1: W+P+T+D
L2: W+P+T
L3: L1-L2 (FAT)

thanks in advance