RISA 3D - Simple Cantilever Beam

[IngeIvan]

Hi,

I am modeling a simple "benchmark" problem for a steel cantilever beam. My question is that in RISA 3D, when modeling the beam with a frame element with one end fixed and the other end free, I get a Cb value of 2.32 (calculated with equation AISC F1-1) taking into account the moment diagram values at the quarter points. From the Steel manual, we know that Cb = 1 for cantilever beams. My guess is that RISA has no way no recognize it is a cantilever as they are all just frame elements and that Cb would have to be manually changed to 1. Is this correct? Is there a way to automatically take this value as 1?

I also noticed that RISA Floor DOES consider Cb = 1, but here I think it is different since you are actually telling the program that portion of the beam IS a cantilever.

Any comments?

 

[mike20793]

I'm sure JoshPlum will have a better answer, but there is no specific command in 3D to define a cantilever like there is in Floor, so you have to tell the program what value to use. Just double click the member and go to the design tab. You will see a box for Cb under flexural parameters.

 

[JoshPlumSE]

You are exactly correct. RISA-3D doesn't know that the beam is a cantilever, but RISAFloor does.

You would want to manually set the Cb value to 1.0 in RISA-3D for cantilever cases like these.