Mark: I think you'll find that SRSS is totally inappropriate for any three
dimensional analysis of any structure with even a moderate degree of plan
irregularity. This results from losing signs when squaring displacement or
force quantities and then taking the square root; signs get lost and result
in very significant errors. We ran comparative test runs using CQC and SRSS
on about eight structures and found that there were still significant
problems with CQC as well as SRSS. I don't think we've yet found an
acceptable modal combination paradigm for all cases.