I am checking a section for flexural rupture [AISC (9-4)] and I am coming up with a different net plastic section modulus than what RAM Connection shows. I believe RAM is taking the gross plastic section modulus and subtracting out the sections of the bolt holes. I used an additive approach following the basic form Znet = Ai*yi + Aj*yj + Ak*yk + ... I also computed the net section properties in an independent section property calculator program and found that it agreed with my approach.
I know that flexural rupture rarely controls and the net plastic section modulus I calculated was close, but not exact to what RAM calculated. Can anyone comment on how RAM Connection calculated the net plastic modulus and where the discrepancy may lie?