Skewed Roller Supports

[PEFLWI]

How do you do skewed roller supports in RISA 3D?

 

[PMR06]

I had to do that once. The only thing I could think of was to rotate the model such that the roller orientation ended up in one of the global axes so the boundary condition worked. I had to change the loading too: components for point loads that sum to the correct vector, distributed loads perpendicular to local member axes (for gravity too). It was a pain! I'm curious to hear if JoshPlum has a more elegant solution!

 

[Lomarandil]

If what PMR is getting into describes what you mean by "skewed roller supports" (which I think it does), the best way I've found to do it (and as I recall, this is what the RISA help file suggests) is using a rigid link between your member being supported and the boundary condition node. You can then rotate this rigid link about its axis to whatever orientation is needed to align with the skewed roller, and release the end reactions of the rigid link to only allow reactions in the appropriate directions.

(I'm realizing this isn't the best explanation, so look up the "Modeling Inclined Supports" section of the modeling tips page in the RISA help file.)

 

[jayrod12]

Lomarandil's suggestion is how I would do it.

 

[JoshPlumSE]

Yes, Lomarndil's suggestion is what I would go with. This procedure is described in more detail in the Help File / General Reference model. Go to the main topic titled Modeling Tips, then go to the sub-topic titled Modeling Inclined Supports

 

[JAE]

Here's a sketch similar to what Lomarandil suggests.

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[JoshPlumSE]

JAE -

Nice sketch.

Dumb question though... how do you embed images directly in your posts? I can attach an image file, but haven't yet figured out how to embed it directly in my response.

 

[JAE]

Josh - next to the little green box for attaching posts is a second green box - click on that one and you can do it.

See below:

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