staircase - rebars for anchoring

[mats12]

Hello, Id like to know how do you guys calculate sufficient rebar for anchoring staircase to concrete slab?

Classic model for staircase design has pinned supports. I understand thats OK since its conservative (regarding reinforcement in the staircase).

But to calculate anchors you need negative moment at the end - fixed support at the end.

Im using model 3 (anchors from staircase to foundation) and model 2 (anchors from staircase to slab).

What do you guys think about this? Any other way?

I know you dont really need anchors based on the original model (pinned supports at the end) but you have to connect staircase to the foundation/slab somehow.

How do you calculate it?

 

[JAE]

For most stairs the rebar quantity is fairly minimal - such as #5 @ 12" o.c. or something on that order.
We usually design for simple span like you suggest but then provide the same, or perhaps slightly less, rebar for the "top" steel at the ends.
This usually suffices and is somewhat rational if you work out the "fixed" end moments and consider that the ends really aren't infinitely rigid...so the moment will be somewhere less than fixed.

You could take a stab at fully modeling the slab AND the end conditions in an attempt to model and mimic the relative rigidities between the slab Ie and the end supports, but in my view they wouldn't usually be any more accurate, or helpful, than the rough method I describe above.


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