The gravity column design interaction equation H1-1a in RAM SS does not account for the Mux/(0.9Mnx) in the unity equation. Why is that ?
What design code year are you using, AISC 360 - 2016? What version of Ram Steel? There have been changes to this approach over the years.
Seth I'm currently using AISC 360-2010 LRFD, and the RAM version is 16.00.01.06 CL
Here's what the 2010 code says (note 2016 is slightly revised)
I believe you are in the rare case where the moment is primarily about the major axis, and the minor axis moments are small enough that you qualify for the use of H1.3 yet the minor axis moments end up controlling. To confirm you can adjust the eccentricity to see at what point the Mry is more than 5% of Mcy and the program will go back to using H1.1a.
Or you can send your file over and I can confirm. I was not able to build a test case that produced this output so far.
Yes, it is controlled by H1.3 but still the H1-1a equation is used to determine the limit state of in-plane instability but I couldn't see ratio of Mux/ Mcx being considered in the equation, it just considers the Muy/Mcy (which it can ignore). I can send the file over please let me know how can I upload? Thanks
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