Manual reinforcement areas

[Anonymous]

I have been attempting to manually add reinforcement to a slab.

The idea is that by provding extra reinforcement we can reduce the maximum deflection on the slab to within allowable limits.

I have selected the whole slab and provided 16mm bars at 150mm centres top and bottom, and in both directions, for the whole slab. This, I feel should be sufficient to significantly reduce deflections.

However, when I run the verification I get the following message "User defined zones do not cover all regions in which reinforcement is required".

I don't understand this as I have definitely selected the entire panel.

I want to be able to view reduced deflections once the additional reinforcement is taken into account, but am unable to.

Advice would be appreciated.

[athurD]

Yi can use file tutorial design.

I is attachment file

[Anonymous]

Hi, I've no problem with actually doing what is described in the attached document. The problem is that when I run the verification I get the following message:

"User defined zones do not cover all regions in which reinforcement is required".

I have checked and I am sure that I have covered all regions with my user defined zones (basically covering the entire panel).

There may be something else that I am not doing that I need to do.

How do I upload the file to the forum as I cannot upload the .rtd file.

Thanks.

[Artur.Kosakowski]

For  smaller sizes zip it. For larger http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Sending-bigger-files/td-p/3795062

[Anonymous]

File can be found here:

http://www.4shared.com/zip/Ob4UFoSW/First_Central_columns_Fully_Re.html

[Artur.Kosakowski]

Try to edit sizes of the zones.

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[Anonymous]

Great, that worked, extending the zones slightly and the error message has disappeared.

However, I'm still having problems - I'm afraid it's baby steps here as I'm still finding my feet with the software.

After running verification now, I get a message saying "for panel no. 1108, the minimum bar spacing:  0.0 [cm] < 2.5 [cm] is exceeded".

I've set my bar spacings throughout the panel at 150mm so am not sure why I am getting this message.

What I am after is updated (reduced) deflections taking into account the additional area of reinforcement. I notice that in the plate and shell reinforcement window, in FE results, I am still unable to select "for provided reinforcement after verification".

Thanks,

Craig.

[Anonymous]

OK, I think I'm making progress. 

I have managed to get a reduced deflection, but now I want to know how to delete a zone, as at the moment I have a zone that I don't want, and I am unable to remove it.

Help please!

Thanks!

[Artur.Kosakowski]

 now I want to know how to delete a zone, as at the moment I have a zone that I don't want, and I am unable to remove it.

Mark it and press the Del key.

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[Anonymous]

Thanks Artur, I'm finally making good progress.

Next question: I have my deflection results. I have deflection of 47mm "for required reinforcement", and a reduced deflection of 12mm "for provided reinforcement after verification".

I would like to know what is taken into account in each deflection calculation? It doesn't make sense to me as it implies that the required reinforcement is taken into account in the 47mm calc. However, I have provided the bare minimum reinforcement and the deflection has come down to 12mm.

Therefore I wonder if the 47mm is based simply on the stiffness of the concrete?

Thanks,

Craig

[Artur.Kosakowski]

I don't have enough information to answer this question. Possibly the required reinforcement is similar to what you defined manually but you also defined top reinforcement (as you have only one zone for the whole slab) in areas that it was not needed (required reinforcement calculated by Robot).

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[Anonymous]

I guess my first question is regarding how the 47mm deflection is calculated. 

The software gives 47mm in two places:

In "Slab - Required reinforcement / Reinforcements / SLS / Deflection U X- Y-"

And "Slab - Provided reinforcement / Plate and Shell Reinforcement / Reinforcement maps / FE results / (U button) / For required reinforcement"

My question: Is this value based simply on the stiffness of the concrete, without taking any of the rebar into account?

Thanks.

[Artur.Kosakowski]

It is based on cracked concrete with rebars considered.

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[Anonymous]

OK, so when I am in the "Slab - Required reinforcement" / "Plate & shell reinforcement" module, and I look at the deflection map, I get 47mm. When I then run verification "with stiffness update" for my worst case SLS combination, my deflection reduces to 12mm.

Now, when I then go to "Slab - Provided reinforcement" / (U button) / For required reinforcement", I get a maximum value of 12mm. Is this the same 12mm as above?

I then add reinforcement manually (16s at 150mm throughout, top and bottom, x and y). I run verification for equivalent stiffness, and my deflection is 43mm.

I then run verification for stiffness update, and my deflection reduces to 11mm.

What does all this mean? 

My thoughts gleaned from your replies and some reading up on the subject:

The initial 47mm is based on an elastic analysis taking into account the required reinforcement.

The 12mm is based on a non-linear analysis taking into account the required reinforcement.

The 43mm is based on an elastic analysis taking into account the provided reinforcement.

The 11mm is based on a non-linear analysis taking into account the provided reinforcement.

Is the above right or wrong, and if wrong, what is actually going on? Can we accept that 11mm deflection, and not 47mm is what the slab is really going to experience? If so we can move forward with our design.

Thanks very much.

Craig

[Artur.Kosakowski]

---

OK, so when I am in the "Slab - Required reinforcement" / "Plate & shell reinforcement" module, and I look at the deflection map, I get 47mm. When I then run verification "with stiffness update" for my worst case SLS combination, my deflection reduces to 12mm.

This may happen as the equivalent thickness is based on scaling displacements and is the estimated method which strongly depends on the way the model is created. The recommended way is to use number of smaller panels with clearly defined support conditions (e.g. one panel per span for multi span slab) rather than a single panel with number of 'internal' supports.

Now, when I then go to "Slab - Provided reinforcement" / (U button) / For required reinforcement", I get a maximum value of 12mm. Is this the same 12mm as above?

Correct.

I then add reinforcement manually (16s at 150mm throughout, top and bottom, x and y). I run verification for equivalent stiffness, and my deflection is 43mm.

That is reasonable - less than 47 mm with smaller reinforcement for the equivalent stiffness verification method with the initial reinforcement.

I then run verification for stiffness update, and my deflection reduces to 11mm.

Again reasonable - less than 12mm for the stiffness update method with the initial reinforcement.

What does all this mean? 

My thoughts gleaned from your replies and some reading up on the subject:

The initial 47mm is based on an elastic analysis taking into account the required reinforcement.

The 12mm is based on a non-linear analysis taking into account the required reinforcement.

The 43mm is based on an elastic analysis taking into account the provided reinforcement.

The 11mm is based on a non-linear analysis taking into account the provided reinforcement.

Correct.

Is the above right or wrong, and if wrong, what is actually going on? Can we accept that 11mm deflection, and not 47mm is what the slab is really going to experience? If so we can move forward with our design.

Yes, but personally I would check the values of deflections using the stiffness update method for other SLS combinations too (to check if your initial assumption of the worst SLS combination is true).

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[Artur.Kosakowski]

Please check http://forums.autodesk.com/t5/Autodesk-Robot-Structural/elastic-and-nonelastic-slab-deflection-verif...

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