Hanging Stairs

[SPruitt]

I am designing a stair system in a building where the intermediate landings are being supported off the overhead steel structure at 3 of the 4 corners. Right now, the detailer shows one of the back corners supported off a seat on a structural column, but is using hanger rods for the other three corners of the landing. Usually, I would add columns where I can or support off the walls, but I can only do this at the first intermediate landing and not at the upper floor landings. If I need to use hangers on 3 of the 4 sides, do I need to be worried about the stability of the structure? I cannot find anything about lateral loading on stairs (other than seismic loading, which I do not have to consider), but I'm wondering if I need to worry about any type of sway due to the flexibility of the hanging rods. The stairs are connected to main structural members at the floor levels. Any insight is appreciated.

 

[JAE]

There will be some sway deflection due to groups of people walking on the stairs and landings - very hard to pin down so I would typically want to provide some means of laterally bracing the landing.

With your one corner connected to the column, that might be enough.

Not sure why you say you do not need to consider seismic. In the US, anyways, seismic is everywhere applicable (even in formerly UBC Zone 0 areas). It may not control portions of the buildings MLFRS but can apply to interior elements - even if it is SDC A with 0.01W.

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[SPruitt]

JAE - thank you for your response. Yes, we have very low seismic so I mispoke when I said I didn't have to consider. Just that it is very low.

 

[MIStructE_IRE]

As with all hanging structures you need to watch for the pendulum effect. Your one corner support (lateral) might do the job but you just need to check it.

 

[Agent666]

Depending on what it's hung from (how much vertical deflection occurs) and the elongation of the hangers, vertical modes of vibration might also be something to investigate.

 

[Ron]

Check for torsion on that one column support....both in the connection and the column.