topic Re: COMPRESSION ONLY supports in Robot Structural Analysis Forum

COMPRESSION ONLY supports

Babak.moussavian — Wed, 18 Apr 2018 08:12:31 GMT

Hi.

In the attached file, I try to create supports as “COMPRESSION ONLY” supports for the foundation (Nodes 1 through 24) in the vertical direction.

The same applies to the walls at nodes 26 and 31 as horizontal springs with “COMPRESSION ONLY” attribute.

It is important that all springs get inactive in the event of tension in nodes.

How can I make sure that the iteration convergence?

Can I enter the subgrade reaction [kPa/m] for the earth and get Robot automatically to compute the appropriate spring stiffness in each node or I have to do it manually?

Kind regards

Babak Moussavian

Re: COMPRESSION ONLY supports

teixeiranh — Wed, 18 Apr 2018 08:19:06 GMT

Is this that you want? I don't quite get it!

Re: COMPRESSION ONLY supports

Babak.moussavian — Wed, 18 Apr 2018 08:48:48 GMT

Hi Nuno Teixeira!

Thanks for your reply.

I want that if the movement of the nodes 1 through 24 would be in the negative Z direction then these nodes should be resisted by the soil. Essentially this would simulate a situation where the soil would be in compression and would be offering resistance and in the event of uplift (tension) the spring stiffness for such tension nodes get “inactive”.

The same applies to nodes 26 and 31:

If the movement of node 26 would be in the negative X direction then the node 26 should be resisted by the soil or else get inactive.

If the movement of node 31 would be in the positive X direction then the node 31 should be resisted by the soil or else get inactive.

Kind regards
Babak Moussavian

Re: COMPRESSION ONLY supports

teixeiranh — Wed, 18 Apr 2018 10:23:54 GMT

You need to select the Unidirectional tab when defining the elastic stiffness of the soil.

Else you could use simple supports on the several nodes that you have defined for your beam.

It is absolutely possible to do that.

Re: COMPRESSION ONLY supports

Babak.moussavian — Wed, 18 Apr 2018 10:43:07 GMT

Could you please modify my model and upload the file?
I am not sure how one can assign compression only attributes to the supports.

Thanks...

Regards

Babak Moussavian

Re: COMPRESSION ONLY supports

teixeiranh — Thu, 19 Apr 2018 09:52:56 GMT

I will post a screencast as soon as I can.

Re: COMPRESSION ONLY supports

teixeiranh — Thu, 19 Apr 2018 12:51:30 GMT

Here it is. You have to define further load cases. But in this video I show how to define it.