Hello all
I am hoping to analyse a reciprocal frame with stick elements (timber beams) mutually supporting each other in a loop.These beams are simply supported at the lower end and “rest” on the next beam all round in a circle (I have attached a photo of a typical reciprocal frame to clarify)
Unfortunately my model is made up of "chunky elements" and “thining them down” doesnt allow to keep overall geometry.
In the robot model called reciprocal 3D I have tried by “bending” beams to fit geometry while in “structure” I have “played” with the connection to work at offset (this doesnt not work though)
I have also attached a flat analysis model in “reciprocal”
Maybe I should be modelling beams as 3D elements? (I have tried this but results are more complex to check!)
I was wondering whether there was an option in Robot which allowed to insert pinned connections at an offset / distance? Maybe I am looking at this in the wrong software?
Thanks
Solved! Go to Solution.
Solved by Rafacascudo. Go to Solution.
Try the following approach:
1. Model the beams as they are in reality (a bar in Robot being the center line of a real beam)
2. Connect 'bottom' and 'top' beams with rigid links defining the master node at the bottom beam and the slave with released rotations at the top one.
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Thanks Arthur
So these rigid links would in effect be "offset" pinned joints?
They should work like that.
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Thanks for your help.
I will try this out and post reply later today or next week.
Regards
When you release rotations for rigid links you should not define bar releases at the same locations. Delete the releases in the model you sent me and you should be fine.
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I am working on a similar structure (see screenshots below) and have read a couple of research papers which suggest that if the top of the members are suitably tied with rigid connections then no lateral thrust should occur at the base. I have therefore modeled roller supports at the base of the rafters but am getting some instabilities and large lateral deflections. Presumably this is to do with the way the top connections / rigid links have been modeled?
can you send the model?
Rafael Medeiros
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Mathematically ,Robot doesn´t accept a 3d structure without horizontal supports even if there will be no horizontal reactions ,like in a lifting situation.
The workaround I use is to set very weak horizontal springs, Doing that you will get the results you expect
Rafael Medeiros
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Do you mind marking Rafael's post as the solution so that it is easier to find? Thank you.
You should be able to press such named button
If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.
I do not have an accept as solution button visible. Perhaps because I commented on an existing thread which has already been marked as solved?
I don't think it is related. I will mark the solution on your behalf and at the same time I'll ask the Forum Team if they are able to find out why you can't see it.
Indeed your assumption was correct. You can't see the button as you are not the person who started this topic. I could move your post and the its answers to a new topic and then you would be able to do this but as your question IMHO is very much in the line with the original topic I'd rather leave it as it it is with the solution marked by myself.
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