1. No. STAAD.Pro designs the section assuming the weld is strong enough to withstand the worst member load.
2. You may consult text books/references on design of built up sections
3. I would avoid using the offsets
4. yes all segments should have KY, KZ, LY,LZ, UNT, UNB considering the way the full physical member is restrained
5. ALL of these parameters should be defined for both columns and rafters
2. You may consult text books/references on design of built up sections
3. I would avoid using the offsets
4. yes all segments should have KY, KZ, LY,LZ, UNT, UNB considering the way the full physical member is restrained
5. ALL of these parameters should be defined for both columns and rafters