BTH-1 Combined Axial and Bending Stresses

[AEng123]

For "3-2.4 Combined Axial and Bending Streses" in BTH-1-2008:

I am being told that when fa/Fa>0.15, I can still just use equation (3-31) instead of (3-29)/(3-30), that (3-29)/(3-30) are optional. The way I read it is that you can only use (3-31) if fa/Fa<0.15. Does anyone have experience with using/interpreting these equations?

Thanks!