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# Re: Curved Stair Stringer

• To: <seaint(--nospam--at)seaint.org>
• Subject: Re: Curved Stair Stringer
• Date: Thu, 25 Sep 2003 10:01:31 -0400

```Is it a one stringer or two parallel stringers?

Regards,

vcernescu(--nospam--at)banerjee.com

----- Original Message -----
From: "richard lewis" <rlewistx(--nospam--at)juno.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, September 25, 2003 9:46 AM
Subject: Curved Stair Stringer

> I looking for some tips for modeling a curved beam. I have an circular
> custom stair. It is supported at the 1st floor (slab on ground) and 2nd
> floor. It looks something like a slotted hole in plan. From the first
> floor it does a 1/4 turn. Then there is a straight run, then another 1/4
> turn back to the 2nd floor. I am supporting it with a tube at the second
> floor and anchoring it to the slab at the first floor. The tube will give
> me torsional resistance. The tube is about 16 ft. long and spans to 2
> perpendicular beams, one at each end. The beams then span to columns
> buried in the wall. Looking at this in plan view the 2nd floor beams
> would form an 'H' shape.
> I want to get feedback for modeling the stringers in a computer frame
> analysis. I guess my first impulse is to use short chord elements to
> simulate a curved member. I started doing this with 15 degree angles for
> the chords.  I would then uniformly load these members and have a fixed
> joint at the tube column at the 2nd floor. I guess the connection to the
> floor slab at the first floor would be pinned.  I would use a moment
> frame from the vertical legs of the 'H' shape to give me lateral
> stability. Any other suggestions for modeling this?
> I am wondering what would be the best section for a stringer.  Since it
> is a curved member it will have torsion.  Should I be using a closed
> section like a tube?  A tube might be hard to bend on the radius.  Should
> I make a closed section from welded curved plates?  Should I just use a
> single thick plate for a stringer?
>
> Rich
>
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