I am having trouble telling RAM where to put a secondary layer of longitudinal reinforcement. If I assign a different value to 2 Layers in the Beam Criteria it appears to assign my values under 2 Layers just to my top bars. I have attached a screen cap of my Beam Criteria and a sheet from my Beam Design Summary to illustrate the issue. I am afraid I might have a fundamental misunderstanding that I can't find a clear answer for in the manual.
Thank you.PDFPDF
In the criteria, the user is indicating where the center of the bar group created from the two layers is estimated (not the absolute location of the 2nd layer). We do this to simplify the design because we can assume the two layers are acting at a particular 'd' value and check capacity without iteration. Then we do a final check to make sure the 'd' value used in the capacity check is not more than the maximum d value that would fit.
This is noted on our Concrete beam FAQ in the section on Effective Depth.
Answer Verified By: Max Karr