AASHTO + Chainlink Fence

[mikeCTE]

In AASHTO section 13.8.2, it discusses pedestrian railings as it pertains to the application of LL and WL.

I am curious about the case where you have a chain link fence that has no top 'rail' - only a tension wire. See attached for example from WSDOT.

The tension wire is clearly incapable of resisting 200lb point load + 50plf for the LL case. Thus, my conclusion is that for the sake of design checks, we should only look at the post and the post should only be sized for the AASHTO recommended 15PSF WL applied to the surface area of the chainlink. I do not think we should apply the LL case on the post.

Is there general consensus on this topic on the eng-tips forums?

 

[STrctPono]

I've often thought about what the 200 lb concentrated load and 50 plf linear load really represents. I always assumed that it was people leaning against the railing/fence and the concentrated load was an impact load case (someone falling into the rail or delivery cart bumping it, etc.) But someone recently on ENG TIPS made a point that it may be for emergency personnel tying off and using it for a rappel point... Not sure how true that is. Either way, even if your tension wire can't "resist" the concentrated load, the fence mesh can and IMO the post still needs to be designed for 200lbs plus (50 plf x posts spacing).

 

[canwesteng]

Is the fence meant to be guarding (to stop someone from walking onto a road for example, and located a suitable distance from the road itself) or fall protection (to stop someone falling off a bridge)? If it's a true pedestrian railing I don't think fence is appropriate.

 

[mikeCTE]

Fence is on a sidewalk, above a retaining wall that is > 3ft fall distance without the fence. The City currently has fence along this area for a mile of roadway. I agree that it feels to me like it should actually be a pedestrian railing, but for the sake of this argument, I'm trying to sort out the loading to the posts.

 

[BridgeSmith]

If I remember correctly, per AASHTO, if it's higher than 5', it's considered a fence, rather than a railing. The railing load is still applied at the 5' height. I also believe that as long as the posts and the fence can resist the loading at the 5' height, a top rail is not required.



Rod Smith, P.E., The artist formerly known as HotRod10