STAAD output is providing me an interaction ratio for a single angle member of more than 2000 for clause H1-1 of AISC ASD code criteria. When I verify this by hand, the interaction of fa/Fa alone is greater than 0.15 which tells me that H1-1 no longer applies and H1-2 should be used.
Does anyone has seen this problem before? Your help will be greatly appreciated! Thanks!
Can anyone kindly reply regarding this issue...
What is the critical condition being reported as? AISC H1-1 or H1-2?
If it is H1-1, take a look at the term "fa", the allowable axial compressive stress. Is it greater than either of the Euler buckling stresses Fey and Fez? If so, (1-fa/Fey) or (1-fa/Fez) is becoming negative which is unaceptable. STAAD may be artificially magnifying the ratio to bring this to your attention. Do you see a warning in the output file that the allowable axial compressive stress exceeds the Euler buckling stress for that member?
If this doesn't help, post your model.
Thanks a lot SKLose, this was really helpful in trying to understand this misleading ratio. The failing clause was H1-1. I wasnt expecting STAAD to "artificially magnify" this ratio. Again, thanks a lot for your time and assistance.