Some issues with the stress amplification factor of elbows?

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1. Sometimes, the thickness of an elbow is greater than that of a straight pipe. There is a stress amplification factor associated with welding pipes of different wall thicknesses, and there is also a stress amplification factor specific to the elbow itself. So, should the stress amplification factors at the weld site of the elbow be added together? 2. CAESAR II comes with its own analysis program for the SIF of elbows; according to this program, if the elbow is equipped with dummy pipes (the program does not specify whether they are leg pipes or horizontal dummy pipes), the SIF of the elbow increases to around 8 – and if the elbow really has such high values, the use of dummy pipes is not advisable. In my understanding, the fake pipe attached to the elbow acts as a reinforcement for it; the SIF of the elbow itself should actually decrease. Could the SIF value of around 8 refer to the stress amplification factor at the weld between the fake pipe and the elbow? The SIF of the elbow’s actual structure cannot be that high. I’m not sure if this interpretation is correct