Concrete Edge Breakout Failure!

[tristan861]

I'm struggling with a steel tube to R.C slab shear connection. I have a 600 kN (Vu) in vertical direction which causes huge failure regarding concrete breakout vertically.

Rods are chemical -post installed- rods (Embedment Length = 300 mm).
Ca1 = 100 mm ( distance from center of last rod to concrete edge).
The slab is already placed.

based on Eq (D-31),ACI 318-11. I have Vcbg = 36 kN only which leads to design ratio of 1660% !! Any idea how to change the concept of connecting to solve this issue?

Please see sketch attached.

Thank you,

 

[structSU10]

Thats a large load to bring into a slab edge with little edge distance. You need something deeper than the slab, or to add a steel member somehow to grab the tube, and the steel can attach to a concrete element with more 'meat' to it.

 

[JStructsteel]

If my math is right, thats 134K? Can you do some bent dowels off the back of your plate and have them take that load in tension and develop into the beam?

I think there is alot more to check, but thats my first thought. How are you handling the bending in the beam?

 

[tristan861]

Its a shear connection.
I cant do anything regarding increasing the thickness of the slab and adding steel column is unlikely.

Can you guys see this proposal? Im wondering if it works

 

[structSU10]

If your slab can handle it, it could. you would need that top plate to be quite stiff. You might be better off just using a bearing type connection if it can figure as the anchors into the slab edge will always struggle to have enough capacity.

 

[BridgeSmith]

I'm not familiar with the equation you're using, so forgive my ignorant question. Is the capacity you're calculating based on the edge distance for the 2 bolts nearest the edge, or is the greater edge distance of the other bolts accounted for?

If you've accounted for the capacity of the bolt group as a whole, you may not have any choice but to change the configuration of the connection. The most effective way I can see would be to extend a plate over the top of the slab (or remove of a portion of the top of the slab to embed a plate or T section) so that it becomes a bearing load on the slab, rather than a shear load on the edge. If that's not an option, extending the connection out along the slab may be the only way.