Stair Stringer Design

[Wrightguy]

Could anyone recommend a good refernce for steel stringer design. It seems there is a de-facto std. using mc12X10.6 or c12X20.7. Has anyone run through these calcs to satisfy a curoisty on limtations of these channels?

 

[civeng]

Hi,
I think one of the best resources are the documents sold by NAAMM (

http://www.naamm.org).

Great and easy to understand documents.

 

[Lutfi]

Stair stringers are not that complex to design. Like you said, the C12 or MC12 are the universal de-facto sizes. They work well with the rise and tread dimensions. They provide flanges for handrail connections.

Loading wise, for a typical stair flight of 4 feet in width, and live load of 100 psf, you are only loading each stringer with 200 PLF. Adding the code required point load (I think is 300 pounds) and apply it conservatively to one stringer. Note that OSHA has more severe loading on stairs for industrial applications than office or residential stairs. Most building codes limit the stair flight to a maximum of 12 feet vertically. Simple analysis will indicate that the 12 inch channels are more than adequate to carry the loads.

Good luck

 

[mrengineer]

Be careful if you have the 12" stringers spanning very far. I have had at least one project where the numbers worked o.k. for both deflection and strength, but stair was still bouncy, and we had to add a couple of posts.

 

[Lutfi]

mrengineer,

Your point is well taken. Human comfort is critical. The way to watch for is to control the span.

Regards