topic Re: Type 1 Instability in Robot Structural Analysis Forum

Type 1 Instability

Anonymous — Thu, 24 Aug 2017 14:31:27 GMT

I'm modelling a floor plate with a core zone. The core is modeled as a series of 1D elements connected to the wind centre via rigid links using the master/ slave function. I am getting type I instability in several nodes but dont want to release their rotation of movement because this will be inaccurate for global wind modelling. Has anyone done this before? I have attached my model.

Thanks

Re: Type 1 Instability

Anonymous — Thu, 24 Aug 2017 14:48:49 GMT

I think you have at least to put Uz supports at the edge of your plates...

Re: Type 1 Instability

Artur.Kosakowski — Thu, 24 Aug 2017 14:53:33 GMT

Hi @Anonymous

I think you should delete your manually defined rigid links and rely on the ones generated by the diaphragm.

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Re: Type 1 Instability

Anonymous — Thu, 24 Aug 2017 15:02:57 GMT

Do I need to do anything different to connect the core walls to the slab so that the loads transfer correctly?

Re: Type 1 Instability

Artur.Kosakowski — Thu, 24 Aug 2017 15:09:37 GMT

Hi @Anonymous

What I proposed should be just enough

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.

Re: Type 1 Instability

Anonymous — Thu, 24 Aug 2017 16:06:57 GMT

OK thanks! When I remove the rigid links the load does not transfer into the core elements through the slab (if i keep the load at the wind centre).

When I apply the load along the slab edge I get the "linear load has not been applied to panel" error. Any ideas?

Cheers

Re: Type 1 Instability

Artur.Kosakowski — Fri, 25 Aug 2017 06:43:26 GMT

Hi @Anonymous

I don't think that the message corresponds to the removed rigid links (in fact the diaphragm automatically generates rigid links and this was why I suggested you to remove the manually defined ones) and as you can see on the picture I attached to my previous post the columns (core walls) deform under the point load applied to the center of the slab.

Could you attach the file with the model where you have this warning?