I was working through design problem #16 of Six Minute Solutions and according to their solution they got a Cm value half of what I got because they said that per 2011 code Cm is no longer limited to a lower limit of 0.4. 2011 code does not explicitly list 0.4 as the lower limit unlike earlier codes but going with Cm of 0.2 gives me a magnified moment that is half of what I got (4400 ft-k instead of 8800 ft-k), which is a huge difference.
The way I got Cm of 0.4 is by limiting my M1/M2 ratio to no less than -0.5 as suggested in Goswami'sGoswami's All-In-One book, which makes sense since the upper slenderness ratio limit would be 40 based on equation 34-(-0.5)=40. My end moments are both equal but are in double curvature.
It doesn't seem right to me that Cm should not be limited to 0.4 as in earlier codes since it can give you a magnified moment half of what you got using earlier codes and this change is significant. What are your thoughts? Have you used Cm of 0.2 recently in your designs?
The way I got Cm of 0.4 is by limiting my M1/M2 ratio to no less than -0.5 as suggested in Goswami'sGoswami's All-In-One book, which makes sense since the upper slenderness ratio limit would be 40 based on equation 34-(-0.5)=40. My end moments are both equal but are in double curvature.
It doesn't seem right to me that Cm should not be limited to 0.4 as in earlier codes since it can give you a magnified moment half of what you got using earlier codes and this change is significant. What are your thoughts? Have you used Cm of 0.2 recently in your designs?
