Design of stair stringer beam

[GodEngineer]

Hi All,

I need to design a 5m span timber stringer beam for a staircase which is inclined at roughly 30 degrees. To calculate the maximum induced bending moment can i just consider the beam horizontal and undertake unusual procedures with the factored dead and live loads.

Cheers,

 

[Ron]

Yes, if you remember that if you lay the stringer flat for analysis, all of your concentrated loads from the treads will be at an angle such that you will resolve the loads into perpendicular and parallel components. Further, your reactions will be angled as well, based on the slope of the stairs.

 

[GodEngineer]

Thank you Ron,

IT worked out well.

Cheers

 

[racookpe1978]

30 degrees is an unusual stairway!

Read your building code again: It almost always requires a very, very specific rise/run requirement, and a specific "maximum step height" requirement. Between the two, you can't make a 30 degree stair legal.

 

[GodEngineer]

Sorry i forgot to explain.

It is an external stairway running parallel to a raised platform held by a 3m timber canti-lever retaining wall giving access to a house up on the platform. The steep inclination of the stairway is required to overcome the high retaining wall.