Reinforcing development

[JStructsteel]

For development lengths of bars that are spaced close together (3"o.c.) what do you consider confinement reinforcement crossing plane of splitting? (ACI 318-14, 25.4.2.3)

I have some #7 bars doweled into a footing. The transverse steel meshes in btween the dowels (top and bottom), and thus steel is crossing the plane of splitting. My edge distance from the dowels to the side of the footing is about 10". Would you consider the transverse bars to be effective to count in the calc? Would you want to see them developed at the edge of the footing?

 

[KootK]

That is a lot of large dowels at a very tight spacing. What is the nature of the situation that creates the demand? Is this some wild, shear friction connection at the base of a shear wall or something?

 

[JStructsteel]

KootK, its a precast pedestal to a footing for a 3 sided arch bridge

 

[BridgeSmith]

So, the dowels are primarily to resist shear?

 

[JStructsteel]

These are tension bars in the face of the pedestal. Shear is resisted via keyway

 

[BridgeSmith]

Which part is the precast?

 

[JStructsteel]

The top part is precast (30" pedestal wall) into a CIP footing form.

 

[BridgeSmith]

I'm still not understanding the aversion to using hooked dowel bars in the footing. You could bump up to a #9 or #10 bar. and have far fewer connections to make.

The other option to consider is to make the pedestal wider to reduce the amount of reinforcing required.

Speaking of simplifying the connections, could you not extend the bars (or anchor bolts) through the pedestal, and anchor them with plate washers and nuts on top.

I would strongly consider precasting the footing and pedestal as a single piece, or doing both CIP. Connecting the dowels to the precast seems like it would be problematic, especially with only 3" c-c spacing of the bars.

Considering the labor and specialty materials required to anchor the dowels in the precast, your most cost-effective solution might be to just pour the footing 30" thicker.

 

[JStructsteel]

I was trying to avoid having 6 different hooked dowel in bar lengths.

The precast is bid and agreed upon. I can do hooked bars, was trying to simplify. Making pedestal wider is not an option.

The pedestal is 7'-6" tall, anchoring into a 30" deep footing. Shipping is not letting me have bars protrude out the bottom of the pedestal instead of dowel bars.

Its sold precast for speed. A single piece in a precast environment still would be two pours. Then weight to ship would be factor.

Hooks is what I will go with, I went down this rabbit hole as i started to investigate straight dowels.

 

[BridgeSmith]

We do multiple length hooked bars all the time. They're much easier to tie in position than straight dowels, anyway.

How are you anchoring the dowels into the precast?

 

[JStructsteel]

Bridgesmith, in the precast, the dowels will be straight. They will be the female. once on site, they will install the male hooked bars.

 

[BridgeSmith]

So, the precast pedestals will be suspended over where the footing will be placed, and then the footing will be poured up to pedestal?

 

[JStructsteel]

Yes, basically. We provide a shell of a form that the pedestals will sit on temporary, then the CIP is poured.

 

[BridgeSmith]

As long as someone is there to make sure the correct dowels get placed in the right locations, which you presumably would have to do for the straight dowels, as well, I don't see an issue with using hooked dowels. I would suggest using larger dowels to reduce the number of dowels and embeds required. You may need to alternate lengths of adjacent dowels, in order to get them all threaded in, though. You should have enough room to do that, though; required hook embedment is much less than for a straight bar.

The other option that may work for you is headed anchor bolts or threaded rods with nuts and washers on the bottom. High strength threadbar, with couplers embedded in the precast, is an option we have used in similar situations. Using 150 ksi tensile strength bars would get relieve alot of the congestion.