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Valued Contributor
jonpople
Posts: 50
Registered: ‎07-04-2013

Rigid Links

234 Views, 6 Replies
09-06-2013 01:42 AM

I am trying to model a slab with varying thickness, so I have offset one of the slabs and then used rigid links to attach the different areas of the slab. I have ticked all of the boxes in the Rigid Link Definition box.

 

Shouldn't this produce a continuous moment in the top of the slab where hogging occurs as the slab has only been thickened below and not on top? I do not understand how the rigid links transfer the moment.

 

Thanks

 

Jon

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Valued Contributor
jonpople
Posts: 50
Registered: ‎07-04-2013

Re: Rigid Links

09-06-2013 01:47 AM in reply to: jonpople
 
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Artur.Kosakowski
Posts: 4,544
Registered: ‎12-17-2010

Re: Rigid Links

09-06-2013 07:12 AM in reply to: jonpople

I do not understand how the rigid links transfer the moment.

 

 

Just  in the same way as very rigid bars with no releases at their ends.

 

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Artur Kosakowski
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Valued Contributor
jonpople
Posts: 50
Registered: ‎07-04-2013

Re: Rigid Links

09-06-2013 07:16 AM in reply to: Artur.Kosakowski

Could you please comment on screenshot that I have posted. Why are the rigid links not creating a conituous moment?

 

Thanks

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pp2008
Posts: 472
Registered: ‎06-23-2008

Re: Rigid Links

09-06-2013 07:19 AM in reply to: jonpople

If any in-plane membrane forces exist in the slabs and they are transferred through the rigid links the moments will not be continuous.

Considering the direction along the connection of panels with different thickness the discontimuity of the moment about this direction corresponds to membrane force perpendicular to this direction multiplied by the offset of panels (the length of rigid links).

 

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Pawel Pulak
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Valued Contributor
jonpople
Posts: 50
Registered: ‎07-04-2013

Re: Rigid Links

09-06-2013 08:37 AM in reply to: pp2008

So the moments that are produced are in fact perpendicular to the direction shown? X is showing Y and Y is showing X?

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pp2008
Posts: 472
Registered: ‎06-23-2008

Re: Rigid Links

09-06-2013 09:57 AM in reply to: jonpople

I was not referring directly to your screen capture because it was not showing MXX or MYY but Wood&Armer moments which are composed of MXX, MYY and MXY so it makes it even more complex.

But the discontinuity is justified even for moments turning around global X on your screen capture (depending on direction settings it can be MXX or MYY).

 

To show it in simpler way below is the bar analogy of this effect in case of 0.1m eccentricity (modelled by rigid link) between 2 bars:offset.png

 

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Pawel Pulak
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