ACI 350 Shear Provisions 1

[profplan]

My interpretation of ACI 350-06, 9.2.6 is that the environmental Durability factor, Sd, does not apply to the concrete shear capacity check, for example, in a sanitary tank wall. That is,
phi*Vc = phi*2*sqrt(f'c)*b*d

I used the above to determine the tank wall thickness which is governed by shear(without Sd). The wall would be thicker if I included Sd. Am I correct? Does the tension hoop stress and bending stresses have any influence on the concrete shear capacity of a tank wall?

 

[JAE]

I thought that 350 specifically excluded shear from the Sd application.

 

[profplan]

JAE - I agree with your thought, that the use of Sd is excluded from the concrete shear capacity determination.
As I am fairly new to ACI 350 provisions, and sanitary structures, I wanted to get some confirmation from engineers who have used the provisions extensively.

The commentary ACI 350-06 R9.2.6.4 seems to indicate that if concrete shear capacity (without Sd) is exceeded, then Sd is used to calculate the additional shear capacity provided by reinforcing. I don't know how you would provide that though in a typical tank wall without some placement difficulty. In, my case, I determined the wall thickness to satisfy the concrete shear capacity using the basic shear equation in the original post (without Sd).

 

[Splitrings]

If I understand ACI350-06 9.2.6 correctly, Sd only applies to the excess shear (above that carried by concrete)carried by the shear reinforcement. I can't see it applying to the wall when no shear reinforcement is used.

 

[JAE]

That's right - I forgot. Splitrings is correct. The Sd applies to the Vs portion of the equation - not the Vc portion.

 

[Splitrings]

profplan,
I certainly don't have extensive experience with 350, especially the -06 code. We design manure storage tanks for dairy farms and in the past have designed to 318. It appears we soon will be using 350. So, I am very interested in the responses also.

Section 11.10 deals with shear in walls, both in the plane of the wall and perpendicular to the wall

 

[profplan]

Splitrings - Thanks for the reference to ACI 11.10 for walls. I also reviewed ACI 11.3 which answers one of my earlier questions regarding the effect of flexure or tension on the concrete shear capacity.

For sanitary tanks, I have been reviewing the PCA publication, Rectangular Concrete Tanks, 5th Ed. It references earlier versions of ACI 350, but not 2006. One of the solved examples states that the "Sanitary coefficient" does not apply to shear.

JAE - Thanks for the confirmation.

Your posts confirm what I thought. Any additional opinions /thoughts are welcome.

 

[NoName1]

profplan,

Related to your question about the tension hoop stress, for walls with "significant" tension forces.

Check out ACI 350-06 11.3.1.3 & 11.3.2

 

[omel18181]

profplan,

while Sd applies only to the excess shear from concrete, note also that Sd does not apply to all load combinations.