Mat Slab Model Review Request

[pncad250]

Being a little green I am unsure of the accuracy of my mat slab/raft foundation model.

It would be fantastic if a savvy user would be willing to look it over to insure that the modeling appears correct and that it is at least creating the correct "Required Reinforcement" output.

Thanks in advance.

[Artur.Kosakowski]

Hi @pncad250

I'd recommend watching the recording of the 5th Robot webinar.

If afterwards you have a specific questions on what you think may be wrong and why just post them as it is hard to review all the model and the output without being familiar with the project assumptions in the first place.

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

[pncad250]

Hi Artur,

thanks for taking the time to respond.

It is a very simple residence mat slab supported on Kz soil, the slab has a series DL and LL loads.

I would greatly appreciate a review to insure that I have modeled the following correctly:

- Kz support of the slab.

- Slab Reinforcing parameters for Area of required reinforcing output.

- and correct FE mesh choice.

Thanks again.

[Artur.Kosakowski]

Hi @pncad250

 - Kz support of the slab

If you expect uplift for any part of the panel change the soil to unidirectional (uplift UZ+ in the soil parameters of the panel thickness). This requires changing the model type to a shell first (Geometry > Structure type > silo)

- Slab Reinforcing parameters for Area of required reinforcing output

Switch off deflection calculations and check panel displacements instead (KZ will govern this) 

- and correct FE mesh choice.

If making it denser will not change the results beyond the limit you decide on (e.g. 3%) it is OK.

In addition there is no load defined in case 3.

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

[pncad250]

Hi Artur,

Thanks for your review, I cant tell you it is invaluable.

Excuse my ignorance:

I did not use the default load "load case 3"  is there any harm in leaving it if not used?

Also, as you recommend - where do I do the following?

Switch off deflection calculations and check panel displacements instead (KZ will govern this) 

Cheers and Thanks

[pncad250]

Hi Folks,

would love to get some direction on this one - call it resolved..

Thanks

[Artur.Kosakowski]

Hi @pncad250

I did not use the default load "load case 3"  is there any harm in leaving it if not used?

No, there is not.

Also, as you recommend - where do I do the following?

Switch off deflection calculations and check panel displacements instead (KZ will govern this) 

See below:

  

If one or more of these posts answered your question, please click Accept as Solution on the posts that helped you so others in the community can find them easily.

[Artur.Kosakowski]

Hi @pncad250

I just wanted to check if you still need any additional help for this topic?

[DennisVDijk]

Hello,

If looked at you model, see fine to me. two points you can look into:

[1] mesh size, start with the thickness of your slab,

[2] use coons, with recteangels for rectangular slab shapes, see below:

maybe your support spring Kz is high, try 1/3 of your current Kz value for a lower bound.

keep up the good work.

Cheers!

[pncad250]

Hi,

I have revised the file accordingly. It has been changed to a Silo 3D object, as a result I have an Instability issue (I have attached a photo).  How do you recommend providing stability without affecting the results?

I have run in to another snag, either the file is corrupted or am doing something wrong.  I am able to Calculate Required Reinforcing, however when I progress to Slab-Provided Reinforcing the page is blank and Calculations button is grayed out! How do I fix this? (photo attached).

I have attached the working file as well.

Cheers hope to hear back soon, trying to wrap this up.

[DennisVDijk]

Hi,

Ignore the stability warning, type 3 can be ignored if the displacement is what you expected.

Your displacement looks fine to me:

[] provided rebar screen: in the required rebar tab you calculate the rebar that is needed. if you have done this, click (on the right) on the button with the concrete beam + rebar. RSA transfers your slab to the provided mode, see below:

a voila. now you ad the rebar, run the verification and you are done 🙂

This is my last day at the office before i go on hollyday. so good luck with your model.

[Artur.Kosakowski]

Hi @pncad250

I have revised the file accordingly. It has been changed to a Silo 3D object, as a result I have an Instability issue (I have attached a photo).  How do you recommend providing stability without affecting the results?

I'd recommend watching the recording of the 16th Robot webinar 

I have run in to another snag, either the file is corrupted or am doing something wrong.  I am able to Calculate Required Reinforcing, however when I progress to Slab-Provided Reinforcing the page is blank and Calculations button is grayed out! How do I fix this? (photo attached).

and in addition to the workflow demonstrated by @DennisVDijk (thank you for your help)  the recording of the 5th one which covers slab reinforcement design in Robot.

Both are available from: https://forums.autodesk.com/t5/robot-structural-analysis-forum/robot-structural-analysis-webinars/td...

If one or more of these posts answered your question, please click Accept as Solution on the posts that helped you so others in the community can find them easily.

[pncad250]

You Guys have been Great.. thanks in advance.  Getting closer!!

Questions;

- when i go to the Slab Reinforcement Screen the 3d image only shows the upper mat of reinforcing in the 12" slab I can't get it to show the lower mat, I have tried toggling the + and - in the upper left hand corner.  What can I do to get it to show lower mat of reinforcing as well?

- I am having a hard time interpreting the provided reinforcement screen, the individual square indicates for example, 0.26in^2/ft and the #5x8.27  does the 8.27 imply 8.27" o.c., this seems to contradict the 0.26in^2/ft. or is this a bar length? (Screen Shot attached)

Cheers P

[Artur.Kosakowski · Accepted solution]

Hi @pncad250

- when i go to the Slab Reinforcement Screen the 3d image only shows the upper mat of reinforcing in the 12" slab I can't get it to show the lower mat, I have tried toggling the + and - in the upper left hand corner.  What can I do to get it to show lower mat of reinforcing as well?

This should switch between the top and bottom reinforcement. If it doesn't try to use these commands:

Reinforcement > Top

Reinforcement > Bottom

- I am having a hard time interpreting the provided reinforcement screen, the individual square indicates for example, 0.26in^2/ft and the #5x8.27  does the 8.27 imply 8.27" o.c., this seems to contradict the 0.26in^2/ft. or is this a bar length? 

0.26in^2/ft is the required area of reinforcement (so 0 corresponds to the part of slab where it is not needed at all unless you want to provide the minimal one).  #5x8.27 is what is proposed for the reinforcement bar diameter you set in the reinforcement type assigned to this panel. This can actually be the value of the minimal reinforcement.

If one or more of these posts answered your question, please click Accept as Solution on the posts that helped you so others in the community can find them easily.