Hello,
I have a question regarding Cb factor.
The question is that "If I design a structure by AISC ASD 9th edition and use defalut cb 1, is it overdesign?"
In case of latest AISC latest code, Cb is calculated as following,
Cb = 12.5 max / (2.5 Mmax + 3Ma + 4Mb + 3Mc)
and in case of ma=mb=mc=max, cb=1
On the other hand, in AISC ASD code (9th edition ASD)
Cb is calculated as following
Cb = 1.75 + 1.05 (M1/M2) + 0.3(M1/M2)^2
and in this case, even if M1=M2, Cb value is over than 1
But In staad design parameter, is shows "Cb default is 1.0"
I feel latest version of default cb=1 seems to be reasonable, (or maybe it can be little conservative value)
but ASD 9th edition case, it feels not. It seems like way over design parameters.
I am not sure I have a right view.
Please give me some advice regarding this issue.
If I design a structure by ASD 9th edition and use defalut cb 1, is it overdesign?