Precast DBA's extending into footings 1

[Samwise Gamgee]

I have a situation where the embeds needed for precast extend into the footing through the stem wall. As the footing is poured first and stem wall is poured after, what is the best way to accommodate the DBA's into the footing.

Can I wrap the DBA's with foam or use sleeves to block-out the areas ?

 

[JStructsteel]

Just develop the DBA's into the second pour, and use the reinforcing from pour 2 into pour 1 transfer the load.

If you leave a void, then it has to be big enough to fill with concrete (how will you know) and then also have some mechanism to transfer the load (shear keys)

Why not just extend the panel down to pour 1, or is that not really to scale?

 

[Samwise Gamgee]

The drawing is not to scale. The precast need to stop 2'-6" from the from the top of the footing. The footing cannot move up due to frost depth considerations. So a stem wall is needed here which has rebar continued into the footing. So there is a continuous load path from Pour-2 to Pour-1

I was going to suggest providing a sleeve and then filling it with concrete.

 

[bones206]

What's driving the length of the DBA's? I'm struggling to understand this detail.

 

[Samwise Gamgee]

They are designing the precast connection to the stem wall to take significant amount of load. As the stem wall is only 10" thick, they cannot make a regular AWS plate with studs work because of smaller edge distances. Its architectural precast and they designed it for in-plane loads (I was puzzled)

I told them the precast connection is not supposed to take much load and just use an embed plate with 4" anchors. They are like, we already fabricated the connections with DBA's .

 

[bones206]

So the DBAs are essentially anchors for a large tension reaction? I assume then that someone determined the length based on developing the reaction force in the bar. If so, adding a bond breaker to reduce the bonded length would reduce its capacity. If this is a critical connection I’d consider lowering the footing elevation to increase the stem wall height. Then design dowels to take the tension from the DBA into the footing.

A grout tube might be an option but I’m not sure they make them that long?