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engr567 (Structural) (OP)
9 Mar 12 14:28
I have a project that involves design of a curve steel stair stringers? How do I start? Help is appreciated!
Lutfi (Structural)
9 Mar 12 16:08
Those are fun. I designed few of them in the past. I recommend using STAAD or similar software tp model the entire stair structural system.


SethGuthrie (Civil/Environmental)
9 Mar 12 16:30
I agree that a Finite Element analysis is great for these, even if you have to model the curve in short segments. Be careful with open sections as the AISC Design Guide for complete warping torsion checks are not part of most packages. If you can use a closed shape (HSS Rectangle) life is easier. Finally, consult with a fabricator or steel bender to find out what shapes can be bent before you go too far. I see advertisers in Modern Steel Construction all the time.
msquared48 (Structural)
9 Mar 12 16:33
I would take a gander with RISA3D here.  Should work well...

Mike McCann
MMC Engineering

Lutfi (Structural)
9 Mar 12 17:10
I must agree with SethGuthroie, use closed steel sections. They work well in resisting torsion. There are specialized fabricators who will bend and curve them and they come out stunning when done. Of course with help from the architect who will cover up the structure.

The links below will take you to two pictures of two curved stairs that were in the same building:

Have fun and nice weekend



JStephen (Mechanical)
9 Mar 12 19:38
"the AISC Design Guide for complete warping torsion checks are not part of most packages"

Just curious on this point- is the design guide in question applicable to anything besides straight beams anyway?
connectegr (Structural)
9 Mar 12 21:59
We design these frequently.  We use Risa, since the design examples for stairs assume they are straight spans.  We typically use plate or HSS material for the stringers.  And depending on the tightness of the curve HSS sections may need to fabricated from plate.  There are several subtle considerations in the design and connections.  An experienced fabricator or detailer may be able to provide some suggestions.  Or, there are designers that have experience in these conditions.

nineninenine (Structural)
11 Mar 12 23:07
Agree with all of the above, this web-site below has some great pictures, reference points for curved staircases:
mijowe (Structural)
13 Mar 12 10:04
not as cool as the post above but...

cool none the less
pwildfire (Mechanical)
13 Mar 12 14:17
We build these from time to time. Steel channel seems to be the preferred material as the flanges help to highlight the helical shape. Typically oversized stair treads are used to help reinforce the stringers. I will say that shop drawings from which fabricators can produce these are a headache. As a starting point you can analyze the stringers as equivalent straight members in combined bending and torsion.
SteelPE (Structural)
13 Mar 12 14:55
I like the part where everyone recommends going straight to software for a solution.  Not that I can come up with a better recommendation.

I have done only one of these and I used tubes as the stringers.

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