RAM steel beam cantilever, Extension or Stub 1

[Huaxingxing]

Hi, I got confused about the RAM steel cantilever function.

Is there any one who can explain this to me? When shall I use extension and when should I use stub?

Thanks a lot,

 

[SethGuthrie]

When you have a beam between two supports with a cantilever use the extension method. The process is to model the span first, then add the cantilever extension to one (or both ends). In this case, the span and the cantilever will be a single beam, a single section used.

When using gravity members, the moments in the cantilever are balanced as moments in the back-span and the support is treated like a fulcrum. When using lateral members, the user controls the fixity at the top of the column so that a fully fixed, indeterminate analysis in Ram Frame can be used.

A stub cantilever, on the other hand, is a cantilever directly from a support, typically a column, with no back-span. This member will transfer moment to the support directly.

Is some cases users want a stub cantilever and a back-span, but using different section sizes. In that case use the stub cantilever method, but make sure to model the beams and supports as lateral members so that you can set the fixity as desired.

 

[Huaxingxing]

@SethGuthrie

Thank you Seth, that's really a good answer.