Steel stair Design 3

[createutoo]

Hey guys
Need some help on designing a steel stair for a bldg in the project that I am working on. I am not civil engineer so kinda lost where to start.
Any input will be highly aprreciated.

Thanks

 

[rowingengineer]

start with dimensions/frame otpions (depending on your situation the dimensions and farming look maybe handled by the architect) and your supervisor.

A clear conscience is usually the sign of a bad memory

 

[createutoo]

Rowingengineer,
the dimensions and spacing are already set by the architect. now I got to size them.
Shall I go to the Codes (if yes which one)?
I think I can design the landing based upon the moment only right?
Then what bout the stringer beam?

Thanks

 

[frv]

You need to get a structural engineer (or at the very least a steel stair vendor) to assist you with this.

 

[connectegr]

If the stair is simple, it can be a catalog item. But if there is anything special, I recommend using an engineer that specializes in this design. Miscellaneous fabricators should have these contacts. Sealed calculations may be required for building inspection.

http://www.FerrellEngineering.com

 

[Brad805]

Many times for conventional channel, pan and concrete filled steps of typical spans, the rise/run defines much of the structural sizing. Just because the loading and span says something like a C6 might work, it does not make any sense to use smaller than a C10 or C12 if the run is 10" or 12".

Start with some basic sections before getting buried in calculations.

Brad

 

[Ron]

Assuming you are in the US and under the International Building Code (or its approved local equivalent).....As simple as a stair section might appear, there are several nuances that can get you into trouble.

The stair section should be analyzed with all loads applied simultaneously. That means the treads are fully loaded (typcially at 100 psf)AND the railing is subjected to appropriate lateral loading (50 plf or 200 lbf applied at any point). Loads are transferred from the stair section to the landings which must also be designed (usually the landing attachment to the surrounding walls is the limiting factor...spans are small).

The simultaneous lateral loading on the railing can be a problem without some lateral bracing of the stringers. Further, the end section of railing is unsupported and cantilevers off the stringer...the top section usually ties back to the other stair section as it turns at the landing, thus providing lateral bracing.

As for member sizes, the most common stringer sizes are MC10 x 8.4 and MC12 x 10.6. Railings are usually 1-1/4" diameter pipe and railing posts are usually 2"x2" tube with a wall thickness of at least 1/8".

Now...back to what others have said...get a structural engineer with experience in this area involved. Stairs are life-safety issues...don't take on that liability without knowing what you're doing.

 

[a2mfk]

In the US it is extremely common for the EOR and architect to delegate stair and platform design to the steel fabricator's specialty engineer. You may not need to do anything, perhaps provide minimum loading criteria (direct from the building code).

If it falls on your lap, I agree with the others, get a structural engineer. Having been the specialty engineer for a steel fab, stairs can be pretty tricky, especially the geometry and fit-up... And sometimes the stinkin' hand rails are the hardest part to make work!

 

[createutoo]

Thanks guys,
This site is really awesome.

On the first post of this string, I meant I am not a structural engineer , but I am a civil engineer.

I try to get somewhere with these info.

 

[Bobber1]

If you are in seismic territory, you may have to have a sliding connection at the base of the stairs so they do not absorb seismic forces and fail, especially if they are part of the egress.

Bob G.

 

[connectegr]

We don't design seismic stairs with free lateral movement. Where most stairs are vertically loaded only. We design stairs with seismic requirements with lateral stability, bracing, moment connections, or connections to the primary structure.

http://www.FerrellEngineering.com