RAM CONCEPT: Large Stabilizing Reaction Floating Loading

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Seth Guthrie — Wed, 26 Jan 2022 21:02:30 GMT

Lateral walls above that transfer to lateral beams which are fully within the slab edge should be fine, but transfer beams and slabs like that tend to be "sensitive" to P-Delta effects. I expect the P-Delta amplification is leading to your inequilibrium. I would run it without P-Delta as a test and confirm if the stabilizing force is reduced. For the purpose of slab design I'm generally a fan of turning off P-Delta. Then turn that back on for the purpose of Column and Wall design.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Max Karr — Wed, 26 Jan 2022 20:28:35 GMT

I was also getting the Large Stabilizing Reaction Floating Loading error for my model where I have lateral walls that have to stop at a floor and transition out sitting on beams. See image below, the two North walls could be modeled as sitting on walls with a very large opening but the South wall has to stop at this level.

I was able to confirm that concept does not like the walls sitting on beams by resaving the model and replacing the beams with walls.

I reviewed the calc log and the large stabilizing loads are fairly small (largest being around 2.7k). Now that I know what is causing it I assume this is a downward load as it doesn't seem to indicate which direction the force is acting. Would it just be a matter of verifying the reinforcing and load diagrams at the effected locations, or would I be missing something if I otherwise ignored the error?

I originally built this model in RSS and imported. I am either on the latest version of all programs or only 1 behind.

Thank you.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Luay Al-Loos — Wed, 08 Sep 2021 00:24:06 GMT

Thank you so much.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Seth Guthrie — Tue, 07 Sep 2021 23:58:05 GMT

To wrap this up, making the walls (or some of the walls) "shear walls" would resolve the stability issue (or you can continue auto-stabilizing it). The reason it matters is because the columns have a bending stiffness factor of 0 assigned, so they are effectively pinned, even though the fixed near and far options are checked.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Seth Guthrie — Tue, 07 Sep 2021 23:01:12 GMT

You should probably just send us your file Secure File Upload or log a service request: https://apps.bentley.com/srmanager/ProductSupport

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Luay Al-Loos — Tue, 07 Sep 2021 22:42:34 GMT

I haven't modified the Balanced loading to be a Lateral SE.

All support columns, the roller far end option is not ticked.

I have only gravity loads.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Seth Guthrie — Tue, 07 Sep 2021 22:31:40 GMT

Have you modified the Balanced loading to be a Lateral SE type? If so, don't do that. Do you have supports below (columns or walls, not all on rollers)? It's OK to Auto-Stabilize a model with only gravity loads, but otherwise ill advised.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Luay Al-Loos — Tue, 07 Sep 2021 22:28:26 GMT

Thanks Seth, much appreciated, if I don't use the Auto-Stabilize structure in the x & y direction, the calculation stopped and the cal. log as seen below

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Seth Guthrie — Tue, 07 Sep 2021 21:28:57 GMT

You can also check the calc log to see how far out of equilibrium it is.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Luay Al-Loos — Tue, 07 Sep 2021 21:20:00 GMT

Thank you very much, Seth, for your advice. I'm running the latest version, 8.02.00.146 x64, I will regenerate the tendons.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Seth Guthrie — Tue, 07 Sep 2021 18:21:13 GMT

That's a little different since it's the Balanced load case. If you are not already running the latest version, 8.02.00.146, try that. Also try regenerating the tendons and check for anything that might be a problem with the tendons (like tendons out of the slab or extreme curvature).

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Luay Al-Loos — Sat, 04 Sep 2021 00:02:08 GMT

Hi Karl, I have two way flat slab problem, I got the following error message in Ram Concept:

" Balance loading has large stabilizing force", would you mind advice to resolve this error, I use Auto stabilizing structure, if not , I got message the structure unstable when I do the run.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Ang Liu — Thu, 16 Nov 2017 14:05:41 GMT

It worked!!! I will have to import new lateral analysis load to run the updated model. Thanks for all the effort you put in Karl.

Other than running it by hand, is there any Bentley program can perform punching check with the situation we have where columns sitting in the wall? Please let me know.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Karl G — Thu, 16 Nov 2017 02:04:29 GMT

There are 3 remaining slab edge segments defined with 0" offset in the model. These are marked in the screen capture below. Replace these segments with slab edge segments with non-zero offsets and then redefine the decks sot that they extend to the new slab edge. This should resolve the problem.

Punching checks in RAM Concept do not account for walls that are connected to the column. The critical section is based on the column shape only. Also, the punching shear stress is based on the column reaction only and excludes any force in the walls. If a punching check is needed at these locations, it would be better to check it outside the program for these reasons.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Karl G — Wed, 15 Nov 2017 20:44:22 GMT

Please upload your revised model for review. I will send you a working model back via a private message.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Ang Liu — Wed, 15 Nov 2017 20:34:58 GMT

I followed all these steps and the error is till there. I do not know a better way to exactly locate the slab edge o the wall/ column surface but I basically set them at non zero. When you do it, did you set the slab edge at a certain point to make it correct? Also with the offset, I saw punching shear issue with columns sitting in the wall, which is weird. Can you advice what to do here? I can reupload the model if necessary. Thanks.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Karl G — Wed, 15 Nov 2017 19:11:47 GMT

The error appear to be associated with the slab edges on the Level C Layout that are defined with 0" offsets and are snapped to the centerlines of beams and columns.

To resolve the problem, replace these slab edges with new ones that have a non-zero offset and redefine the decks so they extend to the new slab edge boundary. In RAM Frame, click on Assign - Nodes - Diaphragm Connection and reassign the Global condition to all nodes. I am not sure why this is required, but I generated unexpected warnings during the analysis if this was not done. After re-running the analyses, reimport into RAM Concept and you should find that the error no longer occurs.

Please post back and confirm that you are also able to eliminate the errors using these steps.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Ang Liu — Wed, 15 Nov 2017 15:41:51 GMT

Thanks Karl. I really appreciate that.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Karl G — Wed, 15 Nov 2017 15:38:47 GMT

The files get uploaded to a folder that can only be accessed by the Bentley team. You will not see the uploaded files here and no other Communities user will have access to them.

I have the files and will review soon. Thank you for sharing them.

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Ang Liu — Wed, 15 Nov 2017 15:34:20 GMT

Thanks for your answer Karl. I have uploaded models thru the link but the files are not showing up here. Am I able to see it here or it is not successful??

RE: RAM CONCEPT: Large Stabilizing Reaction Floating Loading

Karl G — Wed, 15 Nov 2017 14:59:49 GMT

RAM Structural System imports the supports reactions for the lateral loadings into RAM Concept. RAM Concept analyzes those forces using a special self-equilibrium analysis, in which the supports are removed and the floor is analyzed with those support forces in place. This type of analysis requires the forces to be in equilibrium. If they are not, then the program adds stabilizing forces which can significantly affect the forces in the slab. The error that you are seeing occurs because the lateral loadings are not in equilibrium and a large stabilizing force is added. More on the lateral self-equilibrium analysis can be found on the web page below:

RAM Concept Lateral SE Analysis

There could be several reasons for the error. Please share your model using the Secure File Upload link at the bottom of the page and then post back with the file name after it is uploaded. I will review and provide more information on what is causing the problem and how to resolve it.