Provided Reinforcement for flat slab - problem

[Anonymous]

I'm very sorry to come back with the same question. I've got a new project - 4 storeys flat slab RC building. Managed to run the model, got results and then moved on to provided reinforcement for slabs. I defined zones manually and managed to get deflection down. Saved the job hoping to deal with punching shear the next day. But when I opened the file the next day - no results for slab provided reinforcement. This happened 3 times and also it's my 4th job with the same issue. I'm now being told to change the FEA software... Please help.

So far I asked our IT guys to install Robot 2015 which they did. They also gave me a faster computer. Each time I run analysis I save it under new name on C drive as opposite to using our server. I think I must be missing something. I tried freezing the reinforcement as well with no luck. Basically no matter how many times I press save button after re-opening the file there is no reinforcement zones and deflection results.

Looked for tutorials to make sure I do everything in correct sequence but with no luck. Could you please direct me?

Your help would be much appreciated.

[Rafal.Gaweda]

File please.

Plese indicate which panel to check; how to create zones (screen shots or movie appraciated) geometry

[Anonymous]

Rafal,

Please find attached two pdf documents and the file. I appreciate your time.

I tried to be as specific as possible. In the described example the results were there after re-opening the file for the first time. But then after saving under a new name with 'no results' option and than opening the original - no results.

I also attach question about tension reinforcement in flat slab.

I look forward to your response.

Thank you again.

[Rafal.Gaweda]

The sequence is not correct - you have to load RC element then - in this case make doubleclick on Plate1 in Inspector window

[Anonymous]

Rafal!

Thank you ever so much!!! I am very gratefull.

Have you had chance to look at my second question, please (2nd pdf)?

Again, thank you for your time. Much appreciated.

[Artur.Kosakowski]

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Anonymous]

Does this module recognize Multiple Layer of rebars?

From my experience it only make the spacing smaller

[Artur.Kosakowski]

For the required reinforcement you may use the larger value of cover to reduce arm of forces in situation when you know that you are going to have more than one layer of reinforcement. For the provided slab reinforcement only one layer of rebars is generated.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Anonymous]

Artur,

Thank you for your response. I fallowed the steps as advised (no missing reinfrocement anymore :), however, I am still confused as to how to interpret these results.

Referring back to my pdf document: Bending moment to be used for designing reinforcement is 263.0kNm (Y-Y  direction). Based on that, minimum required reinforcement is 4273mm2/m according to Robot. But the hand calc, following BS8110, for the same value of 263.0kNm, effective depth of 260mm and spread over 1m width gives me a value of 2776mm2/m. I am trying to understand how does Robot calculate the quantity of required reinforcement as it seems to be much more than expected.

Thanks again.

[Artur.Kosakowski]

Referring back to my pdf document: Bending moment to be used for designing reinforcement is 263.0kNm (Y-Y  direction). Based on that, minimum required reinforcement is 4273mm2/m according to Robot. 

I assume you refer to the panel 1 calculated for ULS:4 SLS:5 no global averaging of forces

In such case min reinforcement is 390 mm2/m

[Anonymous]

I was referring to required top reinforcement above column. Please see attached pdf.

After lots of thinking  figured that the 4260mm2/m required in Y-Y direction above the column must be based on a bending moment without reduction above the support. But then again while calculating the required reinforcement I ticked the reduction box (as you can see in the pdf) so it shouldn't be the case. I also found this:

http://forums.autodesk.com/t5/robot-structural-analysis/rc-slab-design-reduction-of-forces-above-col...

And that tells me that the reduction is taken automatically when one ticks the box...

Therefore I am not sure why I need 4260mm/m2 and how Robot has actually calculated this value.

Thank you again for your time.

[Artur.Kosakowski · Accepted solution]

Please look at the reinforcement table on the picture in my previous answer. The max. value I got for the model you attached SS019017 - Model 09.09.2014 C.zip ‏2170 KB is similar to what you expected.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Anonymous]

Thank you!

Best Product Support ever!