Stair handrail loading

[enginerding]

The 2000 IBC requires 100 psf for stair loading. It also requires 50 plf for handrail loading and states that it shall be "applied in any direction at the top and to transfer this load through the supports to the structure."

When designing the stair stringer, does the 50 plf handrail load need to be applied simultaneously with the 100 psf live loading on the stair tread?

Related (less important) question: The dead load of my stairs is less than 50 plf per stringer, does the stringer need to be designed for an uplift load (handrail load applied "in any direction") with the compression flange (bottom flange) unbraced because the stringers are connected at a distance from this flange?

 

[NITTANYRAY]

The MC10 and MC12 stringers don't work with a pipe 1 1/2 STD post. I have seen them in the field and the attempted welds would be comical if they were not a critical item.

We specify C12x20.7 for our stringers where handrails will be attached and MC12x10.6 where the handrails are attached to the wall.

For exposed stairs we like to use HSS12x2 stringers.

Actually it is unlikely that the 50 plf horizontal load would be applied to the full length of the handrail. If there are three or more posts supporting the hand rail, I have no problem using the 1/3 stress increase.

What I find surprising is that a lot of fabricators in Ohio use pipe 1 1/4 STD as their generic size when the Architect doesn't specify a size.

 

[WillisV]

FYI the "stair stringer" MC12x14.3 mentioned by Nutte is described in the attached file.

 

[SteveGregory]

We use a C10x15.3 for most stairs. It has a nice 3" flange.

 

[jzog]

As for the MC12X10.6 being too big, don't listen to that person. It's a very common stringer size, and it's one of the lighter channels used for stringers.

 

[archeng59]

I do not apply the 50 plf handrail load simultaneously with the 100 psf stair load since the handrail force is caused by the same activity as the 100 psf loading.

I use C12x20.7 channels for stringers to facilitate welding of handrail posts to the top flange of the stringers. The 12" depth helps reduce bouncing stairs more than the 10" stringer depths.