footing reinforcement

[TXPE4mdc]

Is it necessary to provide additional steel perpendicular to the primary steel in a shallow footing? What section of the code pertains to this?

If the anchor bolt embeddment is sufficient for the tension load based on the failure modes per App D of the ACI 318-05, is additional steel required?

 

[Lion06]

In a spread footing, there is no "primary steel" - there is bending in both directions, therefore you need "primary steel" in both directions.

For a wall footing, where you only have bending steel in the transverse direction, you should still provide longitudinal steel for T&S. This will also help the footing "span" over any soft spots that may be present.

 

[TXPE4mdc]

My reference to primary steel was for bending. There is steel in both directions to account for bending. My question was referring to steel perpendicular to the steel for bending. The footing is 18 deep with anchor bolts embedded 8".

 

[Lion06]

Oh, you mean steel that is parallel to the depth of the footing? There are only two reasons you would need that:
1.) Shear reinforcement for the ftg - this is never done, just size the thickness so you don't need it.

2.) To develop anchor rods. If you're meeting all the requirements of App. D and it works for strength, then you don't need steel parallel to the anchor rods.

 

[EngMarami]

These steel is only required for punching shear in footing (if thickness of concrete is not enough & you can't increase the thickness for some reason).
so in this case you should provide steel parallel to depth of footing.
but anchor bolt is only used for tension and you should provide enough depth of concrete to make the anchor bolt effect.
do we have any code that state using steel parallel to anchor bolts?

 

[Lion06]

EngMarami-

App. D allows you to use rebar to develop the anchor rods in lieu of designing for the concrete breakout capacity. You still have to check the other failure modes - pullout, steel capacity, and side face blowout (if applicable) - but you can get out of the concrete breakout check by providing adequate reinforcement. You need to properly develop the rebar with the anchor rods, but it does come in handy - especially if you have some high moments or uplifts that land on piers and your concrete breakout cone is small.

 

[EngMarami]

Thank you StructuralEIT for your guidance.