RC Columns subjected to shear forces – ACI 318

[Refaat]

Dear Artur / Rafal

Greetings

May I know the reason behind getting very narrow stirrups spacing when I verified it in both (Required / Provided Reinf.) for a simple RC Column subjected to very small shear forces according to ACI 318 ?

And which code formulas does RSA use to calculate (VC – Shear concrete strength & VS – Shear reinforcement)?

Manual Verification According to  ACI318 -2002

  Bar (6) in the attached model as example :

Fc = 24.10 Mpa  ;  bw =200 mm ; d = 600 – 48 = 552 mm ; Nu = 248.96 KN

Ag = 200*600 = 120000 mm2 reduction factor for shear strength = 0.75

11.3.1.1        Vc =  90.32 *0.75  = 67.74 KN > >> 5.31 KN 

11.3.1.2        Vc = 103.70 *0.75 = 77.76 KN >>> 5.31 KN

While as RSA gave me very small stirrups spacing (75mm) as in the pictures

 No need to use stirrups just using minimum shear reinforcement will be enough according to clause ACI 318 (7.10.5.2)

 

         Thanks in advance

          Refaat

[Refaat]

Dear Artur / Rafal

Greetings

Any help will be appreciated

Best Regards

Refaat

[HoshangMustafa]

Hi

Please find the attached file

[Artur.Kosakowski]

Dear Reffat,

HoshangMustafa pointed you in the right direction. Point 7.10.5.2 is not used when you include shear in the design. If this is marked then robot follows:

As the smaller side is 20 cm when you subtract covers and divide by half you will get 75 mm.

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[Refaat]

Dear Artur

Thank you for your response.

May I know which is code clause refer to this condition “Point 7.10.5.2 is not used when you include shear in the design.”?

IMHO this clause ( 11.4.5 ) as appear in the attached picture (1 & 2) should be used only when  the shear reinforcement is required . in other words         when (Vn > Vc ) then Vs  should be used .

Where :

Vn : Nominal shear strength  : Vn = Vs + Vc

Vc : Nominal shear strength provided by concrete.

So, I think RSA has to verify firstly if the applied shear forces can be provided by the concrete only according to clause (11.2).

If so ,   then clause (7.10.5.2) should be used.

If Not , the clause (11.4) should be used and of course included (11.4.5) & (11.4.7).

Best Regards

Refaat

[Artur.Kosakowski]

I think what you wrote makes perfect sense. I have forwarded your comment to the RSA development team. Thank you for your feedback.

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[Refaat]

Dear Artur

Greetings

Because of the importance of this thread. I look forward to give it priority in the coming RSA revision   “2018”.

Best Regards

Refaat

[Refaat]

Dear Artur

Greetings

Because of the importance of this thread. I look forward to give it priority in the coming RSA revision   “2018”.

Best Regards

Refaat

[Artur.Kosakowski]

Hi @Refaat 

Corrected in RSA 2020.

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