Precast Concrete Balstrade subject to Crowd Loading

[asixth]

Hi guys,

I have a balustrade for a stair subject to crowd loading that was initially insitu concrete however, the QS has decided it will be easier to build if it was precast. Personally I don't think this will work because it will be unable to transfer moment into the slab.

Has any had a detail similar to this that has worked? Likewise does anyone have advice on what the best construction solution would be for this situation?

 

[apsix]

Cast the balusrade with cogged reinforcement bars hanging out of the bottom edge.
Prop the precast balustrade off the block wall, with suitable lateral restraint.
Cast the slab underneath it.

 

[Ron]

As long as the ballustrade is anchored at the top ends, it doesn't need to transfer moment to the slab. (assuming you have reasonably spaced columns.

Just load tested one a few weeks ago. I'll look up the results and let you know.

 

[hokie66]

Oh, come on, asixth. This is the balustrade we have been hashing over in your other thread. Don't spoil it all by taking a quantity surveyor's advice on something he knows nothing about. It has to be cast in place. Well, not has to, but precast for your particular stair balustrade is silly.

 

[asixth]

I only have a 4.5" brick vaneer that needs to be supported of the balustrade. The only load path I have is a cantilever. Is there anyway of achieving a moment connection with this detail.

 

[JAE]

The precast balustrade could be cast with rebar coming out of the SIDE at the bottom, along with a corbel like ledge to support the slab.

See attached sketch. There would also need to be some rebar for the balustrade to wall connection. Still some bugs to work out but it could be done. Also, some tweaking of the proportions of the ledge, rebar layout, etc. would be needed - this is just a quick idea really.

Now whether it is more economical and a better choice, I'll leave that to you.

 

[BAretired]

You could use weld plates anchored to the slab and flush with the top of slab. They could be spaced at, say 4' centers. The precast balustrade would have matching weld plates, then you field weld them together.

The architect may wish to add a strip along the bottom to hide the weld plates from view.

BA