Hi,
I have a two story concrete column that is unbraced the full height. Looking at the design results the moment magnification factor (delta) for the top story is 3.8 which I was able to verify by hand using ACI 318-14 Eq. 6.6.4.5.2. However the bottom portion of the column has a moment magnification factor of 17.85, which cannot be verified with that same ACI equation. I believe the program analyzes the two portions as one column, so why are the results that much different? Is this an error or am I missing something?
Thanks,
Shane
Perhaps there is some change in the column (size, f'c, orientation). Regardless why it's happening you should assign the 3.8 factor to the lower segment in Ram Concrete Analysis mode.