Does RISA have a support condition for "bearing only"

[Ron247]

Does RISA have a method to model a reaction that is "Bearing only". It would be like roller, but would not be able to prevent separation from the support. I know I can use Roller and scrap results that wind up needing a mechanical connection but would rather model what I have. I have an older version 14. I only use RISA and nothing beyond 14 at that.

Does any existing program model this reaction condition?

Also, in FBDs, is there a symbol for this bearing only condition?

 

[KootK]

The search term you probably need is something like "non-linear gap element" or "contact surface". I've always found it annoying that such a simple thing winds up inviting so much computational complexity.

To my knowledge, RISA does not have this. That said, a simple way to produce a similar effect might be to replace your support with a one directional spring element, which RISA does provide. Just make it really stiff in the fixed direction.

All of the serious FEM packages will have the feature that you seek. Ansys etc. I don't imagine that those packages would suit your production model though. Some of the production FEM packages do have the feature however. SAP is one example:

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I'm sure that there is a symbol but I don't know what it is. And it would be unlikely to mean much to us FEM-Light modelers. I might just go with something like the sketch below with the gap dimensioned as zero given that my goal would likely be communicating the condition to myself of someone like me in the future.

 

[Ron247]

a simple way to produce a similar effect might be to replace your support with a one directional spring element, which RISA does provide. Just make it really stiff in the fixed direction.

Thanks, I have been functioning with blinders on I guess. That is a simple method and should get what I need. Have not run one yet, but I hope it does not create an instability error. For loads in one direction, I would have only 2 reactions when it is not used but 3 reactions when it is used. Problem with using the roller support, is I can put the load on in the wrong direction and not realize it unless I notice the normally compression members have tension and vice versa.

might just go with something like the sketch below with the gap dimensioned as zero given that my goal would likely be communicating the condition to myself of someone like me in the future.

I think for now, I will just show a rectangle on the ground, similar to using a triangle, and let it denote bearing only. Like you said, the symbol is to pass along how I envisioned the reaction to function to others or to myself in the future when I say, "what the hell is does a square foundation reaction mean?"

Thanks