Cantilever Steel Stairs

[ZimStruct]

Can anyone please direct me to a design guide for cantilever stairs in steel? I'm looking at one at the moment and any help on this topic will be appreciated.

 

[PST09]

I assume you mean a set of 'floating' stairs where each step is fixed at one end like this:?

http://www.marrettistairs.com/staircase/hanging-staircases/metal-steel/fs/sm013.jpg

 

[jike]

Please define what you mean by "cantilever". Stringers, treads, landings, etc.

 

[ZimStruct]

apologies for not being specific.

The stair has no support at mid landing and are only supported at structural floor level i.e stringers are cantilevered off the floors!

 

[Lion06]

Where are you located? I think this is more of a "scissor stair" than a cantilevered stair. I would be concerned about vibrations for this case. The strength design should be pretty straightforward, especially if you can model it in Advanse or Risa.

 

[jike]

These stairs rely both on fixity at the floor levels and truss action between the stringers and torsion in the members connecting the stringers together.

A 3D model should be sufficient for you to determine stresses, rotations and deflections. In addition to 100% loading on both flights, I also recommend using full loading a one flight with zero on the other to look at maximum torsion.

 

[InDepth]

jike is correct. Modeling the staircase as described is the way to do it. Detailing is the next key. If you are in a seismic region or a heavy wind region you will also need to add lateral loads to the model. I would recommend some members be added to the floor framing to drag loads from the stringers into the building diaphragm for gravity and lateral loads.

 

[ZimStruct]

Thanks everyone you for your valuable insight.

StructIET - yes you are right, it is a scissors stairs, I'm based in Eire. The stair is cantilevers off link bridges between two blocks and is a feature in the atrium space.
Done a similar design with a solid concrete stair and followed guidance in Reynold's Concrete Designer's Manual.

 

[PST09]

Reynolds’s Concrete Designer's Manual

That is such a brilliant book! 10th edition should be in every engineer’s library

 

[apsix]

Why? You don't like the 11th edition?

 

[PST09]

I dont have the 11th edition but from what i hear they have cut a few things out of it and its not as involved at the 10th edition?...might just their personal view though!

 

[apsix]

I haven't seen the 10th so I can't judge, perhaps I should check it out.
Certainly the printing quality of the 11th edition is poor.

 

[csd72]

ZimStruct, just use the reynolds book to get your actions e.t.c. and do the rest of the the design to steel codes.

 

[SlenderBeam]

11th edition is not very good at all. I don't know what they were thinking when they printed it.

namely:

1. a lot of good charts are no longer in there (two way plate/cantilever wall charts)

2. a lot of the charts are hardly legible!! it's as though they photocopied the charts.

a poor update.