Steel stair stringer

[StrP88]

May I ask if you have a channel shapes toed outward for stair stinger and on top of them there is handrail attached to top flange, do they see any torsion? Shall I do anything torsional related if there are?

They are straight stringers. Please if you need more info. let me know

Thank you

 

[KootK]

Sort of. The stringers are prevented from twisting by the stair risers and treads in many scenarios. In that case, it tends to look more like cross web bending than overall section torsion. It's not an easy thing to evaluate and, to my knowledge, nobody really does.

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.

 

[KootK]

I've always found it curious that, as a profession, we seem to expend a seemingly limitless amount of effort (Link) considering the handrails and their connections when, in fact, it quite unclear what happens to those loads once they make it into the stringer proper. I suppose that there's some rationality in simply choosing to stop caring once the load moves into more substantial members along the load path.

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.

 

[Archie264]

More likely the handrails aren't really an issue; however, in this litigious age we just need someone official to agree with that. Should there come a time when a governing body decrees that stair stringers must take ____ capacity/magnitude of torsion then we'll endlessly debate how many angels can be loaded, unbalanced, on one side of them.

 

[JTMergens]

In my opinion if you also have steel or concrete treads that are positively attached to the stringers they would brace against torsion and share that load between the two and the stresses are too minimal to consider. Additionally, typically these types of stairs (at least that I have seen) will be with C12x20.7 and typically end up very under-stressed (unless you have an uncommonly long span, but you should have a landing every 12' in elevation unless it's something industrial) and the little bit of torsion from the guardrail isn't enough to have a significant effect.

 

[KootK]

There are two kinds of open riser stairs that I don't like for torsion:

1) Architectural open riser. Not tooo bad.

2) Industrial open riser where the tread is just some marginally connected bar grate looking thing.

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.

 

[SAIL3]

JTM....is there an exception to the requirement of a landing @ every 12' max rise in industrial applications?

 

[jayrod12]

SAIL,

Around here as long as it isn't classified as an egress stair our industrial clients can have a stair of any shape provided it meets their internal safety and ops requirements. They once made a stair that was 8" run and 11" rise and a total lift of 13'-6". It felt like a ladder more than a stair.

 

[thaidavid40]

On open-riser industrial stairs, especially if they will have the "bolt-on" type tread seat angles, we will lace some welded, L2x2x1/4 angles diagonally across the bottom flanges of the stringers, for the very reasons discussed here. We normally won't do that though if the treads are all-welded. Thus far, we've not had any complaints about stair sway, or bounce.

Thaidavid

 

[Ron]

I use 3/4" bar stock to provide side-sway resistance in a "V" or "W" configuration depending on stringer span. The treads brace the stringers from both torsional issues and lateral bracing. The bar stock is there to mitigate a "global" movement of the stringer span. If you do an FEA model of the entire system, you'll see that the bar stock (or angles as Thaidavid noted) pick up a fair amount of load.