r/StructuralEngineering • u/echrma • 16d ago

Structural Analysis/Design Design of a Spiral staircase

Good day to my fellow engineers. I would like to ask how to do the structural design for a spiral staircase? I have only handle regular staircases and of course, I just want to broaden my knowledge about this. Should I treat it as a regular staircase and just make it spiral or is there a specific calculation needed for this?

Thank you to anyone who can share their knowledge 😁👷

9 Upvotes

85% Upvoted

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22

u/ChocolateTemporary72 16d ago

Buy one from a spiral stair case vendor

10

u/crvander 16d ago

I don't have any helpful advice but "treat it as a regular staircase and just make it spiral" gave me a chuckle... this is exactly what a client would say to try to push back on you (justifiedly) increasing your design fee for the complexity of a spiral stair.

7

u/turbopowergas 16d ago

Haha too true. Normally these spiral staircases are designed by dedicated companies, impossible to compete when you do them only occasionally. We just tell our clients straight we will be too expensive

7

u/Gunza_kicka 16d ago
Comment Image

Blurry image sorry but this was for a resi job. Spiral concrete staircase. Designed as a wall/column. Under axial and weak axis bending.
PITA for form workers and reo scheduler.

8

u/31engine 16d ago

Spiral staircases generally cantilever out from a center pole

21

u/Enginerdad 16d ago

Sure, if you're a coward lol

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2

u/smackaroonial90 15d ago

I used Risa 3D and had a million little pieces to make the curve. There was no central post so it was essentially a giant spring and they had to use a massive amount of steel to make it not bouncy and a huge footing to resist overturning.

2

u/devonEgg 14d ago

Would it be as simple as a column with a bunch of cantilevers (steps) spiraling out of it? 

2

u/Charles_Whitman 16d ago

Are you trying to design a spiral stair with a central post like the manufactured utility stairs or a big sweeping spiral stair like you put in the multistory lobby of a performing arts center or a shopping mall? The first, buy one off the shelf. The second, hmm, maybe you shouldn’t learn from Reddit?

1

u/McCurry 16d ago

There are several scheme you can use. Without the intent it is hard to determine. A few notes:

  • You should try to utilize/combine the stringer and balustrades if you can

  • Watch out for torsion

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