Fall Protection Load Rating

[H57]

We have designed a steel beam to use as the anchor point for a fall restraint system. We have designed the steel beam for a 5000 lb static load. The client has asked for a load rating that can be posted on the beam. Should the load rating for this beam be 5000 pounds (static design load) or 310 pounds (assumed weight used by OSHA to determine the use of a 5000# static load) or some other number?

 

[JedClampett]

Since the beam is intended to be used for fall restraint, I would stencil on the beam "Intended for fall restraint anchorage per OSHA." I think that any numerical rating would be confusing.

 

[MiketheEngineer]

BTW - OSHA allows a fall restraint capacity at twice the anticipated load. Its in the code now. With a properly designed shock absorbing lanyard you could reduce the capacity to around 2,000 lbs.

We did the testing and submitted to OSHA. Shock loads were always below 1,000 lbs. They bought off on it and made the change many years ago. Yo-Yo's or self retracting lifelines induce even less force.

We use these on all our scaffolds. There are probably no scaffolds that can survive a 5,000 load. We had a lot of "push back from the scaffold mfgs at first. But at 2,000 lbs - we found just about any part on any system could. But only one guy/gal on one piece at a time.

Obviously, if you have a "save" - you may bend some material and it needs to be taken out service and scrapped. A few hundred dollars of material gone is well worth it.

BTW - our people are trained to "tie-off" the minute they leave the ground. Not doing so - will probably get you fired - That is how strong we feel about it. Actually, our people use 2 lanyards - so that they can hook and un-hook as needed. Does this slow them down?? Yes - a bit - but after they get used to it - you would never really notice any loss in productivity. This includes ladders, decks, etc.

 

[DWHA]

Mike, that is very interesting that you were able to reduce the tie off loads to 2,000 lbs.

You said "WE" did testing. Is this testing published such that is is available for reference for others to use in the design of tie off systems?

 

[Teguci]

Maximum Arresting Force (MAF) for full body harness per OSHA = 1,800 lbs
Typical MAFs for shock absorbing lanyards = 900 lbs

Engineered system safety factor = 2

Worst case = 2 x 1,800 lbs = 3,600 lbs
Typical case (requires control over equipment) = 2 x 900 lbs = 1,800 lbs

I would not publish a load on any of the members for the fall arrest system. It is often more complicated than that. I would consider placing a label on the beam referencing the users back to a drawing with CYA notes on it.

 

[MiketheEngineer]

Teguci has hit it pretty right on - based on our testing.

Yes - it is available - once you are a customer.

This forum is not meant for sales - but we are the largest scaffold provider in the US and our name begins with a B.

 

[ToadJones]

It is usually pretty easy to design for 5000#, might as well do it.

 

[Teguci]

When your competition designs to 5,000lbs its a good thing.

Try putting 2-5,000lb loads at the center of a horizontal lifeline.

I will see your 3/4" diameter cable and lower you to 1/2", much less the ridiculous anchorage you'd have to detail (smile).

 

[ToadJones]

"...Try putting 2-5,000lb loads at the center of a horizontal lifeline..."

To my knowledge the anchor point is to withstand a 5000# load in any direction, not the lifeline.

The cable design itself is another story.

 

[Teguci]

ToadJones,
Sorry for being spunky. My contention with your response is the wasting of other peoples money without due regard (we don't like it when other people do it to us).

There are times when a 5,000lb design makes sense. But we are engineers and have been afforded the use of refinement with a safety factor of 2.

To your point regarding the anchorage, the anchorage of a catenary system (horizontal lifeline being one) will often need to take 6 or so times the vertical load being resisted. Depending on the geometry and loads, the load at the anchorage could be in the 10 to 40 kip range. A reading of OSHA allows laypersons to believe that 5,000 lbs is the magic number and anything designed for 5 kips will provide safety to any kind of attachments (1926.104 comes to mind). Clearly (unless you haven't read it of course) OSHA needs to abolished in its current standard and recodified into something a little more specific and appropriate.

Back to the original post. If I absolutely had to load rate the beam, I would mark it "MAF = 1,800 lbs"

 

[ToadJones]

Let me be more clear.
If you were to directly tie off to say a D-ring, it was my impression that the D-ring has to resist 5000# load in any direction.

Design of centenary systems is altogether different, this I understand.


Not to be spunky myself, but often times designing something to 5000 lbs isn't anymore expensive than 2000 lbs.
I tend not to try to hit the gnats ass when designing things that directly involve sever injury or death if they fail OR are misused.

 

[msquared48]

Toad:

I have to agree with Teguci here. I commonly use 1800 pounds too, and it is a dynamic, not a static load. I have all sorts of approved proprietary connectors using this figure.

With wood roof trusses, the 5000 pound figure is going to be a
B)(*& to generate an anchor for.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[ToadJones]

Understood....I usually dealing massive building columns.
Sorry for the tunnel vision.

 

[MiketheEngineer]

Not too many scaffolds or roof trusses - I am well versed in both - would be able to take a 5,000 lb point load!!

Check out a 1.9 x .125 steel tube 10' long or a 2x4x 8' long. Not gonna make it!!

 

[JStephen]

One issue is that the 5,000 lbs (or whatever number it comes out to) needs to be the strength of the beam, not the safe lifting capacity, so it could be very misleading to label the beam in that way- you may have someone hanging a hoist off of it and lifting 5,000 lbs in the future. If the labeling is specifically desired for fall protection, it would be better to spell out the assumptions made in the design (ie, one person, using model XYZ lanyard, etc.).

 

[IFRs]

I would stencil it "Designed for one worker tie-off" or something to that effect.

 

[msquared48]

I would also add "Please place around neck".

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[MiketheEngineer]

m^2

We tried that. The workers got a bit nervous and OSHA couldn't understand it.