1910.25(b)(6) Stair Tread Load

[larsacious]

OSHA States the following in section 1910.25(b)(6):

Each stair can support at least five times the normal anticipated live load, but never less than a concentrated load of 1,000 pounds (454 kg) applied at any point;

However, if you review the McNichols stair catalogue that follows the NAAMM standards, the Bar Grating Stair Treads are designed for a 300# point load.

Has anyone resolved the discrepancy? The NAAMM is an industry standard that is used on almost all industrial stairs and yet it seems they do not meet the OSHA point load requirement.

 

[JStephen]

I am looking at the McNichols catalog. They use 300# to establish the maximum tread length. So yes, you may require a tread length shorter than their maximum length.
They also limit loading based on deflection, which is not an OSHA criteria.
Also, in the OSHA load above, the 1000# would be an ultimate load, whereas the 300# is allowable-stress load.
Lastly, "anticipated live load" distribution is not necessarily the same as McNichols.
Check the bar grating design notes- I think the ratings are just based on 20,000 psi allowable bending stress, so it's not too hard to re-calculate as required.

 

[IFRs]

The McNichols load may be on a few of the bearing bars, the OSHA load is on all of them?

 

[271828]

My understanding goes along with JStephens.

Check the 1000 lb without an ASD factor of safety.

You'll never get anything reasonable to work otherwise, and millions of these stairs are in service.