Kinked Steel Stair Stringer
Kinked Steel Stair Stringer
(OP)
I have a question regarding kinked stringer design. The NAAMM standard for metal stairs design kinked steel stringers based on a uniform load that is projected along the length of the stringer. When I look at a kinked steel stringer it appears that there would be an outward thrust at each end of the steel stringer.
What would be the correct way to design a kinked steel stringer? Is there an industry standard regarding designing for the thrust?
Thank You,
Val
What would be the correct way to design a kinked steel stringer? Is there an industry standard regarding designing for the thrust?
Thank You,
Val






RE: Kinked Steel Stair Stringer
There is a thrust due to live load due to the end restraints, but live load deflection usually controls my stringer designs. And I think it is conservative if you look at the stringer as taking all the vertical load in bending.
To be exact, you would have to analyze it as taking combined bending plus the axial component plus thrust for the sloped part, then bending plus thrust for the horizontal landing part. But I just keep it simple and use what has worked for thousands of stringers. I flatten it out and check stresses and deflection for bending.
RE: Kinked Steel Stair Stringer
For this reason I would recommend analyzing the stringers as simple beam (as if there is no bend in it).
RE: Kinked Steel Stair Stringer
RE: Kinked Steel Stair Stringer
Val Courtney, PE
Valstone Engineering, Inc.
RE: Kinked Steel Stair Stringer
'Bringin' the mullet back into style'
RE: Kinked Steel Stair Stringer
RE: Kinked Steel Stair Stringer
Also ensure that the stringer is laterally restrained at the point of the kink ohterwise it will just tend to twist.
RE: Kinked Steel Stair Stringer
I'd be less worried about the thrust and more worried about the kink. How do you design the kink? I know how I'd do it but most stairs I've seen are not reinforced at the kink (or knee). Maybe I'm missing something.
RE: Kinked Steel Stair Stringer
RE: Kinked Steel Stair Stringer
Val Courtney, PE
Valstone Engineering, Inc.