Waste Slab Stairs Reinforcement 2

[stattik123]

In a waste slab stair, the bars directly underneath the steps; what are their purpose and what are they usually called?

 

[hokie66]

"Waste slab"? What do you mean? A picture might help.

 

[stattik123]

Waste slab stair is the typical stair with your riser and your goings/thread... the reinforcement directly below the steps... what purpose they serve and what are they called?

 

[hokie66]

I'm guessing that you mean "waist slab" instead of "waste", and that is only because I googled it.

The reinforcement types in a stair slab are top, bottom, and distribution. The purpose is to reinforce the stair slab, similar to any structural flexural element.

 

[Tmoose]

As OP does not see value of a picture, I went a-Googling for one.

Maybe E1 and E2 here ? -

http://www.acivilengineer.com/2013/04/typical-reinforcement-placement-of-rcc.html

 

[KootK]

Maybe the sometimes controversial nosing bars?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[stattik123]

@kootk.... I have seen various types of reinforcement in stairs within the waste slab region.... but the puzzling question is; do you think that all of these different concept of reinforcement in stairs waste slab are correct?

 

[KootK]

Probably not but I'd need to see a sketch of the arrangements that you're concerned about before I were able to pass judgement intelligently. The vast majority of the time, I see it looking as shown in TMoose's link. In North America, stair reinforcing details tend to look very similar to the details shown in the old CRSI manuals which, presumably, is where folks picked them up in the first place.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[stattik123]

@Kootk.... Here is an image of a stairs that is reinforced ..... what are your thoughts on it ?

 

[KootK]

It looks spot on to me. If you straighten out the stair and rebar in your head such that is becomes a horizontal member, you'll find that the reinforcing disposition is pretty much like you'd expect in any normal slab or beam.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[stattik123]

@KootK ..I like your perspective never thought of that before.... So the extra bars in the stairs reinforcement are for extra over support?

 

[KootK]

So the extra bars in the stairs reinforcement are for extra over support?

Exactly. The top steel is there in anticipation of hogging moments near the supports. I always find things a little confusing at the landings. For example, in the photo that you posted, I doubt that little support beam at the bottom right really offers much torsional resistance. As such the waist slab is probably in positive bending almost all of the way to the wall. The detailing usually ends up supplying both top and bottom steel in these areas so we're probably covered either way.

I'd never heard the term "waist slab". Always good to learn something new.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[stattik123]

@ KootK with all of that said what would you recommend to mitigate against that positive bending straight to the wall?

 

[KootK]

I would. However, that appears to have already been done.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.