Free-Standing Stair
Free-Standing Stair
(OP)

Hello Engineers,
I have a steel freestanding stairs to design, is there any additional consideration I have to take into account rahter than designing a simply supported stairs? is it right that I need to apply 2-3 live load cases to give max tension in higher flight and max compression in the lower flight.
Thanks for any help or recommondation






RE: Free-Standing Stair
RE: Free-Standing Stair
And the connections at the ends may not be correctly modeled as an infinitely rigid end boundary constraint - for example - the top two may be connected to a floor beam which has flexibility to some extent. That needs to be included in your model.
Also - you need to check the vibration of the assembly - making sure to keep the frequency as high as possible - i.e. definitely > 5 Hz but higher would be preferred.
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RE: Free-Standing Stair
RE: Free-Standing Stair
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.
RE: Free-Standing Stair
Emergency exit access also will get running and crowding conditions you'd not normally see.
RE: Free-Standing Stair
Dik
RE: Free-Standing Stair
When checking dynamic behavior - any pin supports can be probably be now considered to have some rotational restraint.
Do you have folded plate treads? As Koot eluded to, this will increase system stiffness. Do the stringers have any welded upstand plates attached? This again will increase stiffness.
Can you put some hangers at the free end of the stair? Belts and braces solution if you get stuck.
RE: Free-Standing Stair
RE: Free-Standing Stair
I'll second everything above, and add that part of our solution was making the header beam supporting things at the top stiff vertically, studs into the slab to resist lateral loads at the top, cantilevering the upper run through the header down to the landing, and a decent sized footing at the bottom such that the lower run could be modeled as cantilevering out of the slab on grade up to the landing. The resultant stairs were sound underfoot without looking stocky, and the concrete filled pans stiffened everything laterally.
YMMV...