Free standing Stair 3

[melsawaf]

hello everbody

i need to design a free standing stair for the first time anybody can help me please ??

 

[CELinOttawa]

Four to six columns, and a whole lot of beams... Including two designed to be inclined.

That response should make just about the same amount of sense as your post.

 

[KootK]

Freestanding = cantilevered mid-landing? Steel? Concrete? Wood? Is it an architectural staircase or an industrial element? Post a sketch and some details and we'll help you sort it out.

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.

 

[racookpe1978]

Another good rule to follow in designing stairs: If the stair go up a level, then the top has to be equal to the higher elevation minus one step height, and the bottom step should be one stair step higher than the bottom elevation. Reverse this if the stair go down. 8<)

More seriously, What country? What rules? What Codes? What material? What does the architect want? What does your boss want?

 

[msquared48]

Is the stair system to be made with donated material and labor since it as to be free?

Mike McCann, PE, SE (WA)

 

[jike]

Not sure what you are describing..... "Free standing" sounds more like completely independent of the adjacent structure for stability. This can be done with two or more columns for "winder stairs".

If you mean "free floating", there are many ways to accomplish that depending on materials, span, appearances, etc.

 

[oldestguy]

I got it. Wants to build one as a stairway to the stars, probably in Hollywood. Maybe rent one of those needed for an airplane away from the gate situation. Less liability risk than depending on our gang here.

 

[melsawaf]

The stair is concrete...in ksa
3 landing
One starts from ground up to 1 m
2nd goes from 1 m to 3m level
The last goes to first floor
Supported on on founation and the first floor
Height is 4m
No columns
Width is 1.4 m

 

[KootK]

Basically, this is a long slender Simple span beam with some kinks in it. It may require some vibration attention. What are your questions specifically?

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.

 

[melsawaf]

Shall i model it in sap2000 as one element

Or

Cantilever landing from foundation to level 1
And another cantilever from first floor to level 2

These cantilevers carring the mid landing

 

[jike]

This sounds more like a non-conventional stairs. More like an ornamental one (with no columns).

I did a similar stairs years ago where I cantilevered the first stair run out of the basement slab with a thickened foundation. You can also cantilever the other runs (down and up) out from the intermediate floors with the landing connecting the ends of the cantilever runs. Make sure you control deflections and vibrations.

I seem to recall that the cantilevered stairs between floors at Peachtree Plaza had a concrete handrail around the outside which provided considerable stiffness.

It is just a matter of detailing it properly. If it is your first ornamental stair design, you should have a senior engineer reviewing and approving of your design work. Since the reinforcing is critical, I also recommend on site inspection of reinforcing before pouring any concrete.

 

[jike]

Not sure that you can do this with no columns since you have 3 landings and no intermediate floors. Your description sounds like you have just a basement and 1st floor. How can you support the intermediate landings?

A sketch would help us understand your problem.

 

[CELinOttawa]

You can do this, and I have done so, but it is a detailing challenge. Also, your landings are NOT to be detailed as standard stairs would be, but instead all of your "turns", ie: landing to stair joints, must be specifically detailed like a beam-column joint.

Sketch out the forces at the landing to staircase interface. They are fun! Also, you cannot get away very thin in this case and actually support the floor loadings a staircase is normally required to handle.

Possible, challenging, and not for the faint of heart. Also, you really must charge appropriately; I charged five times my normal hourly rate, and I was only *just* happy... Liability like mad!

 

[KootK]

You could model it either way OP, so long as you can deal with all of your support forces appropriately. You might consider a "spine" beam underneath your stairs to address all of the detailing concerns raised above.

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.