Hi fellow stressers!!!

I am doing a comparison between one beam element software and Caesar II regarding code stress check for EN 13480.

I have come across this feature in the other beam element software as stated below:

"The program assumes that the greatest range is caused by the difference between no-loads-status and the defined
load case, if this is not true, e.g. in bypass systems the stress range is defined by the difference between NLF possible load cases, combined in one load case group."

I have noticed also in their code stress formula they get the difference between two moments e.g inplane moment is shown like this "(iiMij-ikMik)^2" where j and k are load cases.

Please share your interpretation of the statement above regarding greatest stress range. I'm confused why there is a need to get the moment difference (e.g for thermal expansion between i and j load case).

Thanks in advance!!