Handrail 200 lb. concentrated load, is there a built-in safety factor? 2

[onlineeng]

When designing handrails with the 200 lb. c.l., does the allowable stress need to be divided by 4? Or, can the moment caused by the 200 lb. load be compared to the yield allowable of the material?(Florida, to conform to FBC.) Thanks in advance.

 

[JLNJ]

I had a glass handrail manufacturer place a 200# horizontal load on his in-place guardrail and wanted to use that as demontrating compliance with the code-required load. This makes sense on its face, but there are additional safety/load factors which come into play. (I don't know of a Code provision for in-place testing.) He also didn't bother contacting us to ask where the load needed to be placed, and he placed it bewteen posts where there was convenient load sharing.

To me it is odd that the handrail provisions, so long a part of the code, are still open to so much interpretation. In my book OSHA is largely to blame because the CFR for this is poorly worded and confusing.

 

[Ron]

slickdeals...HVHZ provisions only apply to wind loads.

 

[JStephen]

I meant to do some more research on this, and kind of let it get by.

In general, if the load is a specified load from a building code and just referred to as a "design load" or something of the sort, then I would agree it would be be designed just like other members of the building or whatever it's on, as noted in the other posts above.

In looking at the OSHA requirements, they say the handrail is to "withstand" a 200 lb load, and of course, don't specify any design code or method to be used for it, and that leaves it fairly unclear. OSHA also specifies a 2"x2"x3/8" angle or member of equivalent bending strength, or a 1.5" "nominal" pipe, which they interpret elsewhere to mean 1.5" OD. Anyway, using 2"x2"x3/8 posts, I think gives 24,000 psi if the load is on a single post. Using 1-1/4" pipe gives 36,000 psi or so. In both cases, that would seem to exceed allowable AISC-ASD stresses, but does not calculate as a failure, either.

I'm not sure where the "should not fail" wording comes from, if anywhere.

The NAAMM publication mentioned above addresses the question on pages 15 and 16, with the authors agreeeing with the other posts above.

 

[nutte]

The 1/3 stress increase for ASD was removed in the IBC 2009. I don't know if the FBC has caught up to this yet. If not, it's just a matter of time before it does. I'd suggest not relying on this stress increase.

 

[a2mfk]

You've mentioned OSHA a few times, make sure the owner does not intend to use any part of this assembly for fall protection tie-off... That is 5000lb!

 

[MiketheEngineer]

Actually OSHA also allows "twice the anticipated load" for tie-off or 5,000 lbs. This helps when using yo-yo's or shock absorbing lanyards which really lowers the forces.

BTW - I have two pre-teen grandkids that could shred a handrail rated only for 200 lbs - and they are not even close to being over weight - just a bit active. Come to think of it - my 4 year g-daughter could probably do it on her own!!.

 

[BAretired]

Sounds like a dangerous four year old.

BA

 

[MiketheEngineer]

She is absolutely fearless!! Jumped into the deep end of the pool last week. At least she had enough brains to get to the side before everyone rushed over.

I call her a SHE-DEVIL. Terrorizes the 8 and 11 year old. 1 year old just cringes and screams when she comes near.

 

[Ron]

Mike...get her into engineering! The profession could use a few like that!

 

[onlineeng]

Thanks, all, for the excellent information.

Thanks for the heads-up re fall protection tie-off, a2mfk. Not an issue here, thank goodness. Now, MiketheEngineer's 4-year-old granddaughter sounds like a force of nature that no amount of engineering could protect against.