I recently upgraded to the latest version of Staad Pro V8i Select Series 6 20.07.11.33. When I run a simple moment frame the rafter now fails in slenderness. I am using the Canadian code.
The model is a 62' wide frame with 21' tall columns. both columns and rafters are W24x68. The columns and rafter have UNT, UNB and LY parameters set to 5'. In previous versions of the software this works great. In the latest version of the software, the rafter fails at 1.93 FR with a Slenderness clause. It has the KLR set at 385. It should be 32.
I tried using the older Canadian 2009 code with the same incorrect result.
If I manually break the rafter in 5' long segments, then the correct failure results are shown.