Primary and secondary beam

[Michele100100]

Hello everyone,

I'm modelling a timer roof structure. I have primary beams, for example 120x240 mm beams with on top of those a smaller beam for example 50x50mm, orthogonally. How can I do it in a way I will have a good moment diagrams?

Some kind of rigid link? or easiest way?

Thanks

[Rafacascudo]

In the picture , it doesn't look like 50x50 , but anyway, it seems the secondary are continuous beam transmiting horizontal shear on both directions but not any of the moments.

. I would use a rigid link ,master node on primary beams up to the secondary ,fixed for the translations and free for the rotations. Probably in the beams end you will also have to fix the torsion rotation or it wiĺ give you instabilties

[Michele100100]

Hello,

Yes, the upper beam is continuous. and yes, is not 50x50, was only a imagine from google. Anyway, I will try how you say and let you know.

Thanks

[Michele100100]

And what about the offset command? it is the same?

[Rafacascudo]

No , in this case offsets would just put the beams in their correct relative positions . But then ,you would  need to use bar releases to not transmit the moments to the primary beams

[Michele100100]

hh ok,

I tried with offset, because in my model Im not able to create a node where the secondary continuous beam cross the primary beam underneath. Should I need to model the secondary beam in different pieces?

Anyway, in the imagine is shown the situation with not offset and not rigid links. (Element, Releases and Moment diagram). The TR 5x10 in the reality are on top of the timber 12x20. With those realeses could be a reasonable diagram of Moment?

Thanks

[Michele100100]

This is with offset, and looks like more correct.

[Michele100100]

In my case, I would like the secondary beams behave  as  a continuous beam on different support.

[Rafacascudo · Accepted solution]

A long bar can be divided in many bars and both models will have the exact same results. You don't even have to divide it in many pieces in order to create nodes where you want/need. Just create these nodes where you want along the bar. You can even use the "divide" tool  to do it selecting to not divide the bar in many pieces.

The bar will be divided internally by RSA , which will create"invisible" calculation points after the model is generated.

I suggested the "perfect" model ,with rigid links option. But it can also be achieved with offsets and bar releases.

But depending on the loads you have and the precision level you need on the results , even a simple model with all bars in the same level will be enough to give you reasonable results