Inrational required reinforcement

[horviadi9]

Hi,

I have some problems with the required reinforcement calculations. I'd like to get the req. reinforcement of a slab based on the russian standards. So I set the russian standards as current setting in the preferences. I chose the RC floor as a member type for the slab. The problem is that my concrete grade is B30 (acc. to Snip) but my reinforcement should be A500HW (acc. finnish standards) or any other which yield strength is 500 MPa. Snip doesn't have this steel grade. In order to be able to choose this, I changed the basic setting of the reinforcement bars in the job preferences so I could choose a 500 MPa bar in Member type tab. I've run the calculation acc. to the russian code (B30 concrete, 390 MPa steel) and the 'mixed' code (B30 concrete, 500 MPa steel). All the other settings were the same. The result of the required reinforcement is about 2 times more in the 'mixed' variation, although the bars are "stronger'. It doesn't make sense to me. How can this be possible? Thank you for answer in advance.

Br,

Adam

[Artur.Kosakowski]

My assumption is that we discuss SNIP 2.03.01 -84 code here. I do not feel like being expert but my assumption is that this code instead of having a formula that allows for calculation of design strength value of steel based on its characteristic one refers to some table which directly gives these values instead. Due to the lack of the formula Robot 'does not know' what to do with the unknown steel (in other words only the steel grades provided in the code are correctly supported). I think that there are also other parts of the code that says for steel grade xxx (enumerative list) the following rules should be applied without any information what to do for grades different than listed.

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[Valensas]

I think we have the same problem as we do calculations with Ukraine code - check the calculation report, text part - Beam/ Column note and you'll see that reinforcement strength is taken as 225 Mpa if you choose 500 grade and strength is 365 if you choose lower AIII grade.

I don't know how to work further as we work on big and important project in Ukraine and we can't prepare design report for local expert.

[Artur.Kosakowski]

As far as I know there is no Ukrainian concrete code in Robot. Do you use SNIP or SP with user reinforcement bars defined (or reinforcement bars database that is different than the default for that code)? 

[Valensas]

we set regional settings to ukraine, but in fact we use SNIP code for design and any reinforcement database wich has 500 grade bars (DSTU, EC, SP). Or we add user reinforcement with 500 strength. In all cases strength is taken as 225 Mpa in calculations.

[Artur.Kosakowski]

Let me try to explain that again.

My understanding of the situation is that contrary to other design codes SNIP does not use the formulas which include steel grades but has got  some predefined tables which tell you what value of a particular type you should use for particular steel grade.  These tables are limited to number of steel grades only. If you introduce a steel grade not described in the SNIP code you no longer can use the tables the code provides and Robot assumes some defaults. In other words you are 'outside' of the SNIP code provisions and the code doesn't tell you what is the right procedure for steel grades different  than included in the SNIP code itself.

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.

[Valensas]

In snip reinforcement принимается в пределах от A 240 до A 1500 grade steel, so 500 grade is not out of scope of standard. Maybe it's because Robot uses old version of SNIP, or maybe there is only mistake in calculation algorithm inside Robot. Either way we can't proceed.

[Artur.Kosakowski]

Send me the sample rtd file with the element you want to design and the screen capture that illustrates the situation you described please.