Fall Protection - Ladders - Evaluate Loading for Ladder Rung
Fall Protection - Ladders - Evaluate Loading for Ladder Rung
(OP)
Our company is considering purchasing a flexible cable fall protection system. The manufacture requires the climbing structure be capable of supporting the loads imposed by the system. For calculation purposes the required bracket load may be assumed to be distributed evenly between the number of rung attachments. The load required for each rung for a single user system is 1,125 lbs. per rung (3,375 lbs./3).
The load required for each rung for a four user system is 2,100 lbs. per rung (6,300 lbs./3).
From my machinery's handbook, would the rung be evaluated as simple supported at both ends with a load at center or fixed at both ends with a load at center? Our completely different calculation?
One of the rungs appear to be 3/4" diameter rebar, 13.5" in length.
Stress at Center (supported), -(W*l)/(4*Z)
W=2,100 lbs.
l=13.5 inches
Z= (Pi*d^3)/32 assuming 3/4" diameter = 0.0413 in^3
Stress at Center = -(2,100*13.5)/(4*0.0413)= 171.6 KSI?
Doesn't appear possible to use the system?
Other opinion?
The load required for each rung for a four user system is 2,100 lbs. per rung (6,300 lbs./3).
From my machinery's handbook, would the rung be evaluated as simple supported at both ends with a load at center or fixed at both ends with a load at center? Our completely different calculation?
One of the rungs appear to be 3/4" diameter rebar, 13.5" in length.
Stress at Center (supported), -(W*l)/(4*Z)
W=2,100 lbs.
l=13.5 inches
Z= (Pi*d^3)/32 assuming 3/4" diameter = 0.0413 in^3
Stress at Center = -(2,100*13.5)/(4*0.0413)= 171.6 KSI?
Doesn't appear possible to use the system?
Other opinion?






RE: Fall Protection - Ladders - Evaluate Loading for Ladder Rung
RE: Fall Protection - Ladders - Evaluate Loading for Ladder Rung
What allowable are you camparing your stresses against? You may be able to take a stress increase for the nature of the temporary load.
It might be optimistic to rigidly fix the ends unless they tie into something quite stiff.
RE: Fall Protection - Ladders - Evaluate Loading for Ladder Rung
RE: Fall Protection - Ladders - Evaluate Loading for Ladder Rung
RE: Fall Protection - Ladders - Evaluate Loading for Ladder Rung
I have no idea what the set-up of the system you are looking at is, but is there a reason it needs to be attached to the centre of the rungs? You can lower the bending stresses considerably by placing the brackets off centre.
RE: Fall Protection - Ladders - Evaluate Loading for Ladder Rung
Wouldn't this over estimate the safe allowable load?
RE: Fall Protection - Ladders - Evaluate Loading for Ladder Rung
-T
Engineering is not the science behind building things. It is the science behind not building things.
RE: Fall Protection - Ladders - Evaluate Loading for Ladder Rung
RE: Fall Protection - Ladders - Evaluate Loading for Ladder Rung
Remember - during a fall - one guy will often pull another guy with him or knock him off also.
That said - you or the mfg should test the thing. We have found that our equipment will hold the loads but can get pretty bent up and must be discarded.
RE: Fall Protection - Ladders - Evaluate Loading for Ladder Rung