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robmirgga
Posts: 15
Registered: ‎08-07-2012
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Reciprocal frame on Robot

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01-25-2013 03:30 AM

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.

 reciprocal 3.pngstick elements not intersecting.JPGconnections using rigid links.JPG

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

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Artur.Kosakowski
Posts: 4,544
Registered: ‎12-17-2010

Re: Reciprocal frame on Robot

01-25-2013 03:47 AM in reply to: robmirgga

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.

 

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.



Artur Kosakowski
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Contributor
robmirgga
Posts: 15
Registered: ‎08-07-2012

Re: Reciprocal frame on Robot

01-25-2013 03:52 AM in reply to: Artur.Kosakowski

Thanks Arthur

 

So these rigid links would in effect be "offset" pinned joints?

 

 

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Artur.Kosakowski
Posts: 4,544
Registered: ‎12-17-2010

Re: Reciprocal frame on Robot

01-25-2013 03:54 AM in reply to: robmirgga

They should work like that.

 

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.



Artur Kosakowski
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Contributor
robmirgga
Posts: 15
Registered: ‎08-07-2012

Re: Reciprocal frame on Robot

01-25-2013 04:43 AM in reply to: Artur.Kosakowski

Thanks for your help.

I will try this out and post reply later today or next week.

Regards

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Product Support
Artur.Kosakowski
Posts: 4,544
Registered: ‎12-17-2010

Re: Reciprocal frame on Robot

01-28-2013 12:33 AM in reply to: robmirgga

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.

 

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.



Artur Kosakowski
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Contributor
robmirgga
Posts: 15
Registered: ‎08-07-2012

Re: Reciprocal frame on Robot

01-28-2013 12:13 PM in reply to: robmirgga

Fixed!

Thanks for your help!

Roberto

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