Adding plates to a beam model 2

[SR71B]

I have a beam model now I need to add a plate. Picture a house. The beams are the 2 x 4 and the plate is the sheeting.

When I add a part and define the elements as plates, apply the beam offset, solve, only the plate is solved. What I am missing?

 

[GBor]

Are only the plates solved or are you only displaying the plate results. Beam results have their own menu option. Look under "Results: Beam and Truss". You should have various options.

Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group

 

[SR71B]

Um, maybe everything is ok. I did look under the the beam results menu. Is there anyway to see the result of both together. We are interested in the rotational displacement and stress value.

 

[GBor]

There really isn't. It would be difficult to see the results with both dithers at the same time.

At locations where the beams have nodes attached to the plates, the displacements are equivalent (guess this is obvious). Stresses in plates and stresses in beams are two different "animals", so to see them at the same time would be more confusing. Bending in beams is a matter of Mc/I where bending stresses in plates are much nastier partial differential equations.

Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group

 

[SR71B]

Is there a way to align the nodes of the beam to the plate?

Will the reported beam stresses and displacement be with or without the plate?

 

[GBor]

There are several ways to align the nodes of a beam and its associated plate. To name a couple:

1) (this one is a bit obvious) When you specify the mesh on the plate, make sure you divide the beam into the same number of segments as you built the plate.

2) Divide the line that makes the beam and use the "Point Move" feature to lock the beam nodes to the nearest plate node.

3) A little more complicated: If your beam cuts across elements of your plate (instead of being aligned with an edge of the plate or a row of nodes on the plate), copy the beam to the same part number as the plate and then use the CAD Geometry tools to "Intersect All". This will cut the beams by every line that crosses it. The reason for the copying to the same part as the plate (notice I said "COPY", not "MODIFY PROPERTIES") is so that your new line created by this copy will also be split and insure that you have complete elements on your plate. One problem with this: If you cut across the corner of a quad plate element with part of the beam, you will end up forming a 5-noded plate element, which is not acceptable, so you will have to look at the plate when you are done and make sure that there are only 3 or 4 noded elements.

Hope this helps.

Garland

Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group

 

[SR71B]

Thanks Garland. It appears that I am heading in the correct direction. I was using your #2 solution.

What about the results - does the plate have an affect the stress indicated in the beam results. It current does not, but it is probably due to not enough nodes aligned to transfer load.

 

[GBor]

Once the beams are properly connected, they will influence one another. Stresses are displacement-dependent and displacements are determined from stiffnesses. The stiffness at a node is determined by the plate properties AND the beam properties using an equivalent stiffness of the beam/plate combination.

If you take a plate and stiffen it will a grillage of beams so that it looks like a waffle and pressurize the plate, the resulting deplacements will look like a sheet draped over a clothes line...it will sag between the stiffeners.

Hope this helps!

Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group

 

[zcp]

It will sag between stiffeners if you break the plate (and beams) into enough elements between stiffeners. Then you can check to make sure you have the applied pressure in the correct direction by seeing which way the plates "point" on the displacement plot.

ZCP

http://www.phoenix-engineer.com

 

[SR71B]

Ok, we have the plates and beams working together now. The next question is, have we modeled this correctly?

To simulate the nailing of the sheeting to the 2 x 4, we have spaced the nodes on the beams and plates to match the spacing in production. Results seem to correlate the model to our testing. Now we want to look at adding an adhesive to the joint.

Do we model the adhesive as a plate and customize the properties to match the adhesive? Do we need to move to non linear?

 

[zcp]

You may have to submodel a 3D joint if you are looking for adhesive forces, etc. What specifically do you want to model with the adhesive / joint?

ZCP

http://www.phoenix-engineer.com

 

[GBor]

Agree with zcp. Modeling an adhesive isn't quite as easy. You will likely have very non-linear properties, so you may have to go the non-linear route. Non-linear analysis gives you some additional material models that are likely to be better suited for the adhesive.

Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group