Wood post at corner of exterior slab

[JStructsteel]

So i have a post at the corner of a building, and the exterior slab is almost flush with the edge of the slab. Is it better to hold the footing down, pour the slab over top of the pedestal, then install the post base? Only issue is uplift. Was thinking a couple #5 bars into the slab and into the pedestal.

EDIT: I will probably call out a deeper embed for the anchor.

Thoughts?

 

[XR250]

@JS,

Seems like a lot of concrete and steel to hold up a wood post. Is this normal where you practice?

 

[phamENG]

JStructsteel - to XR250's point, at a height:width of 1.6667:1 this would qualify as a Pedestal under the plain concrete section of the code. So as long as you don't have seismic concerns that preclude plain concrete, I'd approach it that way.

It might end up requiring that anchor to be set in the footing, but there will be a lot less going on there. Or, just a single bar to handle the tension from the anchor down into the footing. I do that on single family houses. Plain concrete for compression, and the minimum amount of steel required for tension.

 

[XR250]

Around here it would be a thickened slab and call it a day. I assume he has frost issues.

 

[phamENG]

Agreed on both. In Ohio, so frost is likely. Even so, the reinforcement is a bit much under a wood post unless it's for seismic considerations.

 

[JStructsteel]

Thanks all

Min bearing pressure, so min footing size for me. Also, min pedestal size, as they more than likely wont get it rightly centered. It is carrying a good amount of load for a wood post.

TBH its more of a standard detail, I would hate to have 1 footing w/o reinforcing, and the contractor start questioning every footing and if it needs reinforcing.

Depth is for frost.

Its a commercial building.

 

[phamENG]

Commercial or not, plain concrete is permitted if you don't have seismic. Whole chapter in ACI 318. And if I were the contractor, I would absolutely question rebar in a 30" footing. What is it doing? You can't develop a #5 bar in 12 inches, so it's not really doing much. Certainly isn't resisting a full FyAs, so I hope you're not expecting it to.

 

[JStructsteel]

Thanks. I guess I am covering my min As required.

My question is more about the slab/post/anchor detail, and I think you helped me with that.

 

[phamENG]

That's my point. You don't really have your 'minimum As required'. If the bar isn't developed, it's not being used in the concrete. That's why I use plain concrete for every footing less than 3' in width. Unless you start putting 180 hooks on all your footing bars, you can't develop it and use it as reinforced concrete.

And hey...you know you can't post a detail and not get it picked apart.