RSA How to join beam structure and panel.

[Anonymous]

I am using beam elements to build a model of a telecomunications tower. But i am not sure if this is completely correct or accurate in structural terms or so.

I mean, when i activate the "structural view" the joints of the different beams look like they just overlapped. I dont know if this just looks this way but the structure is solid and well joint. 

I also would like to know what happens if i try to fixed this structure made of beams to a plate because when i draw a beam element it is just a line (the Center line), and then i specify which are the sectional properties of that beam element. But when i have to join a beam to a flat surface, i dont know if i have to use a support or a release, neither where or how to set things so half of the beam´s body does not overlap with the flar surface.

I attached some pictures for you to see what i am talking about.

I can not seem to find a way to know how the software interprets the union of two beam elements in a specific node, like in the first picture i attached. Neither what happens when a Beam "goes through" a surface.

I need to understand how this works because this tower is fixed to a flat platform, which is just a plate of steel welded to some L shape beams and i can´t think of other way of doing it.

Thank you very much, this is my first time using RSA, sorry if my questions are too basic.

Hope someone can help me out.

[Rafal.Gaweda]

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Khristopherson wrote:

I am using beam elements to build a model of a telecomunications tower. But i am not sure if this is completely correct or accurate in structural terms or so.

I mean, when i activate the "structural view" the joints of the different beams look like they just overlapped. I dont know if this just looks this way but the structure is solid and well joint. 

Just "look". FEM calculations operates on "stick" model connected in nodes.

I also would like to know what happens if i try to fixed this structure made of beams to a plate because when i draw a beam element it is just a line (the Center line), and then i specify which are the sectional properties of that beam element. But when i have to join a beam to a flat surface,

Look here: http://forums.autodesk.com/t5/Robot-Structural-Analysis/Beam-offsets/m-p/3332921/highlight/true#M276...

i dont know if i have to use a support or a release, neither where or how to set things so half of the beam´s body does not overlap with the flar surface.

I attached some pictures for you to see what i am talking about.

????????????????

[Anonymous]

"Just "look". FEM calculations operates on "stick" model connected in nodes"

What does this mean?

 I am going to draw this thing and put it all together, once i have it, i´ll show you which my problem is. I think that is the least of my concerns for now.

But i have another question, regarding the same project.

In the picture below you can see tower i have to model. 

I built the tower and and got some results but now i need a better and complex model, I want to simulate more realistically the way the parts of the towers are all kept together. This is done using a cable-pulleys system. The self weight of the tower elements keeps the tension in the cable so the tower does not move.

I found that i can simulate cables in RSA, but the examples that i found were all of a single cable that keeps one element fixed while holding it to the ground or something like that, and i need a way to simulate the one cable that passes through several pulleys and hold all the 6 parts together. I would really appreciate if you guys can help me with this by giving me some guidelines or ideas on how to do this.

Thank you very much for your help. I hope you can help me because I really need to model those cables to have this done by this weekend lol.

[Rafal.Gaweda]

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Khristopherson wrote:

"Just "look". FEM calculations operates on "stick" model connected in nodes"

What does this mean?

This is what you model for calculations, example:

I built the tower and and got some results but now i need a better and complex model, I want to simulate more realistically the way the parts of the towers are all kept together. This is done using a cable-pulleys system. The self weight of the tower elements keeps the tension in the cable so the tower does not move.

I found that i can simulate cables in RSA, but the examples that i found were all of a single cable that keeps one element fixed while holding it to the ground or something like that, and i need a way to simulate the one cable that passes through several pulleys and hold all the 6 parts together. I would really appreciate if you guys can help me with this by giving me some guidelines or ideas on how to do this.

Thank you very much for your help. I hope you can help me because I really need to model those cables to have this done by this weekend lol.

Rather hard or not possible to calculate in automatic way.

I guess you have to calculate forces in \ from pulleys manually then apply them to model with cables.

[Anonymous]

I thougth of something but i dont know if this could work.

What if i place some isolated nodes in the "working space", in the place where the pulley is supposed to be, and then i place fixed supports in these nodes. Then i put a beam with cable properties connecting this support with the tower part. In terms of mechanical vibrations this could be a good approach/simplification. I need to do something close to reality because i also have to see what is the maximum nodal load that i can put in the tower without having it crashed.

I also thought of placing rigid links connecting each part of the tower, so the software could intepret it as if all the parts were held together and so i could obtain results for my modal analysis. But when i see the modes, i can see the shpes of the modes of vibration, but the rigid links stay in their place, what does it mean?

Same thing happens with the static case, the tower seem deformated but the rigid links dont move with it.

I attached my model to see if you can help me or recommend me what to do to make a better simulation.

[Rafal.Gaweda]

I also thought of placing rigid links connecting each part of the tower, so the software could intepret it as if all the parts were held together and so i could obtain results for my modal analysis. But when i see the modes, i can see the shpes of the modes of vibration, but the rigid links stay in their place, what does it mean?

Same thing happens with the static case, the tower seem deformated but the rigid links dont move with it.

It is correct. Rigid link is artificial connection between nodes - not displayed displaced on deformation or mode diagram.