Minimum Shear Reinforcement in Pile Cap 1

[arbitrader]

ACI 318 - 11.5.5.1 States that a minimum area of shear reinforcement shall be provided in all reinforced concrete flexural members (prestressed and nonprestressed) where factored shear force Vu exceeds 1/2 x Phi x Vc;

except:
(a) Slabs and footings;

Do I interpret this to mean that in slabs and footings minimum shear reinf. is not required unless Vu>Phi x Vc?

 

[WillisV]

Correct. Elevated reinforced slabs as well as spread footings can take up to PhiVc with no shear reinforcing (as are almost always designed this way). For the instance of a PileCap however note that PhiVc can be used as much higher than 2sqrtf'c due to the deep beam shear effect of a low depth to span ratio. See CRSI provisions for more information on that.

 

[arbitrader]

Thanks so much WillisV for your clarification.

It is my understanding that shear as high as 6sqrt(f'c) is allowed subject to the Deep Flexure Member shear equations that consider Mu and Vu at the critical section.

 

[WillisV]

No Problem...allowable shear stress can actually go up to about 12sqrt(f'c) depending on conditions per CSI provisions (which ACI references for pilecap design and are therefore allowable by code for design). Theoretical pure shear is up at 32 I believe.