Ram Elements vs Risa 3D vs spMats

RE: Ram Elements vs Risa 3D vs spMats

Seth Guthrie — Fri, 04 Aug 2017 22:03:35 GMT

I don't typically and Ram Elements does not either when it reports area of steel required for shells due to out-of-plane bending. I've only ever considered torsion according to Wood-Armer methods in Ram Concept where that program does it automatically. Even in Ram Concept I would only do this for some irregular system where slab torsion was a significant concern. For a bit more information see: https://communities.bentley.com/products/ram-staad/f/ram-staad-forum/103137/ram-concept---beam-torsion?ReplySortBy=CreatedDate&ReplySortOrder=Ascending

RE: Ram Elements vs Risa 3D vs spMats

Malton Prifti — Fri, 04 Aug 2017 19:04:05 GMT

I am using Ram Elements. My local axis are aligned to the reinforcement and to the M11 and M13 moment.

In Ram Elements, are you saying I don’t need to add the moment from M13 to M11 and M33 (using Wood and Armer method) to calculate my flexure reinforcement?

Thank you for the quick response,

Malton

RE: Ram Elements vs Risa 3D vs spMats

Seth Guthrie — Fri, 04 Aug 2017 17:59:37 GMT

Use M11 and M33 directly, assuming the shell 1 and 3 axes are aligned to the reinforcement (or whatever it is that you are checking)

RE: Ram Elements vs Risa 3D vs spMats

Malton Prifti — Fri, 04 Aug 2017 16:10:02 GMT

Does Ram output M11 and M33 with the contribution of M13 by default? Or should the absolute value of M13 be added to M11 and M33 when determining what moment to use for flexure steel design?

Thank,

Malton

RE: Ram Elements vs Risa 3D vs spMats

Max Karr — Fri, 21 Apr 2017 14:10:28 GMT

Yes I did eventually find that that was the assumption in the help manual but was waiting on your confirmation. So thank you for that.

RE: Ram Elements vs Risa 3D vs spMats

Seth Guthrie — Fri, 21 Apr 2017 13:59:49 GMT

If the reactions are the same, but the contours are different, and less linear then I would agree. We use thin plate assumptions. You can read more about that in the program manual pdf (search for thin plate).

RE: Ram Elements vs Risa 3D vs spMats

Max Karr — Fri, 21 Apr 2017 12:48:07 GMT

Thank you for your reply Seth.

To my knowledge, yes this is the plate elements and not the footing module. I don't believe we have a license for the footing module.

Unfortunately I do not know Ram Elements enough to argue the difference in the meshing or the additional supports, other than I know the other engineer set the model up with the same mesh distribution and I can verify that the corners are pinned.

I've been checking the other contours, and while the values are off the contours themselves are similar in appearance as they should be.

I think it may come down to what type of plates the programs use. A link was shared with me on eng-tips.com that compared Risa with a thick plate modeler against two thin plate modelers (Risa being a thick plate modeler). The FEM stresses in the thin plate models were higher, and from skimming the results the differences were along the lines of what I am seeing between Risa and Elements.

So the question then is, what type of plate does Ram Elements use?

RE: Ram Elements vs Risa 3D vs spMats

Seth Guthrie — Thu, 20 Apr 2017 20:52:44 GMT

This is in the main Ram Elements analysis using plate elements, not the footing module I assume.

One factor could be the meshing of the plate or the addition of extra supports. For more on this see: communities.bentley.com/.../ram-elements-shells-faq

Besides M11 and M33 moments, Ram Elements can also plot Mmax or Mmin moments (or Von Mises stresses) to capture the absolute worst case. For more on those check the program help pdf (search for Von Mises).