Steps in structural slab 2

[canstructural]

Hi,

Please see the attached sketch and comment on acceptability of the rebar details at step location. All suggestions are wellcome. I need to know if someone has practically done any other detail for large spans and for steps larger than slab thickness.

 

[haynewp]

I would anchor the vertical bars on the left face of the step closest to the exterior up into the top of the upper slab, similar to the way you have anchored the diagonal bar into the upper slab. The step will have to transmit moments between the 2 slabs.

 

[mtu1972]

I don't see that your tesion steel is lapped correctly. I would try to lap the "Z" bar from bottom steel to bottom steel. If possible I would also try to widen the transition zone through the step to flatten out the bends in those bars.

If stress reversals are possible, from patterned or vehicle loading I would also try to lap top steel to top steel in a similar fashion.

GJC

 

[paddingtongreen]

My question is: is the slab supported on the near and far sides? if it is the step is going to behave as a beam. Otherwise, I agree with mtu1972, vertical bars are not developed.



Timing has a lot to do with the outcome of a rain dance.

 

[miecz]

Agree with haynewp that the leftmost vertical bar needs to be hooked at the uppermost level. Otherwise, its not developed at the mid level of the vertical element. Although the right vertical face is presumably in compression, I would develop the rightmost vertcal bar in the same way. With those bars properly developed, you can eliminate the diagonal bar.

 

[canstructural]

Thanks for your input.

See attached sketch.

 

[Teguci]

Yup, option 2 does it.

 

[JLNJ]

The 10" depth might not be enough to develop the Z bars. Be careful with these inside corners.

 

[canstructural]

JLNJ
What if you have 6" sawtooth stairs for say 15' span.

 

[paddingtongreen]

canstructural, with steps, you make the underside a continuous sloped line, no breaks in the tension rebar.

Timing has a lot to do with the outcome of a rain dance.

 

[Galambos]

I'm sure you have already thought of this, but would you consider making the slab step into a beam if you're concerned about the transition?

 

[apsix]

paddingtongreen

I'd be interested in seeing that detail.
I can't see how it can be done. Or perhaps only when you have a very long transition, ie. a shallow slope.

 

[hokie66]

apsix,

I think you misunderstood paddingtongreen. He is talking about typical stair slab framing in answer to canstructural's post.

 

[swazimatt]

a little off-topic, but how do you analyse the moments in that portion of the slab?

 

[msquared48]

Very carefully?

Mike McCann
MMC Engineering

 

[apsix]

hokie

Yes, you're correct. I missed the embedded question.

Attached shows how not to reinforce stairs.

 

[msquared48]

So, then it would be better to slope the backside of the step at 45 degrees or so to allow the tension bars of the slab to function...

Or, literally turn the step itself into a concrete beam with the slab spanning to the top, and to the bottom of the beam.

Mike McCann
MMC Engineering

 

[canstructural]

Step can't be made as a beam, it is continuous without any support.

apsix,
I think the sketch you attached is for information only, it can't be built like that. You need closed hoops or other rebar arrangement for continuity.

See sawtooth stair design chart as attached.

 

[asixth]

canstructural,

can you please inform us on what the plan looks like becuase in the transverse direcetion that step is going to behave like a beam.

As already has been posted you will need continuity of the bottom reinforcement.

 

[Teguci]

Love the MC Escher stairs!