Fixed Ladders - Side Rail Stiffness 1

[Maturin]

I am designing a 30' ladder (approx) that will not have any intermediate supports along its height. Is there a rule of thumb regarding the required stiffness of the ladder side rails to satisfy serviceability requirements (i.e. ladder does not shake or sway excessively to cause discomfort to the climbers).

 

[fegenbush]

As my preference, CC.1.1 and CC.1.2 of ASCE 7-05 are good places to start. L/360 for vertical deflections that are walkable and L/500 for horizontal deflections. Perhaps someone else has a better suggestion.

 

[racookpe1978]

Start with - but don't stop there! - at the minimum OSHA requirements for 200 lbs force (up, down, sideways) of the handrails at 36" above tread height at the most critical point (the point furthest from any support) of your system.

Apparently, this will be midpoint of your railing.

This temporary (overhaul or construction) or permanent?

 

[Maturin]

Thanks for the responses.

The ladder (not handrail) is a permanent installation and is replacing an existing ladder. The ladder sway that workers are currently experiencing is in the plane of the ladder (i.e. parallel to the rungs). Out-of-plane direction is not a problem.
The current side rails are C6x8's and the slenderness in the strong axis is approx. 177. If the rungs rotate on the channel web (i.e. no Vierendeel action) then the slenderness ratio in-plane is much higher. Probably a safe approach would be to match the slenderness for both the strong and weak axes and not consider any strength contribution from the rungs.

 

[JStephen]

The problem I've run into there is that you can assume the ladder hangs from the top support, in which case, very little stiffness is required to meet the strength requirements- you could use a rope ladder. The channel stringers sound like a reasonable approach. If they are not doing the job, then it may be advantageous to mount a conventional ladder on a larger beam, rather than making the ladder itself stiffer. Ideally, you'd want to be able to grasp both the rungs and the stringers while climbing.

 

[Maturin]

Thanks JStephen.

The beam with a standard ladder is a good idea that I hadn't considered.

 

[SAIL3]

FB 2 1/2x2 1/2x3/8" @ 10' max support
Angle 2 1/2x2 1/2x3/8" @ 20' max support
C4x5.4 @ 30' max support...
these are are as old as dirt