Live load on chain link fence

[bjren]

In AASHTO LRFD Section 13.8.2:

“The design load for the chain link or metal fabric fence shall be 0.015 ksf acting normal to the entire surface”

How was this load derived? It doesn’t make sense to apply it to the entire surface no matter what height of the fence is. (For example, 10 ft high chain link fence over the bridge). Live load is live load. No matter what type of the fence is, the total applied live load should be simillar, correct? Should 0.2+0.05L be the maxium live load for the chain link fence post design?

 

[bridgebuster]

I don't think so. Railing is intended to be more robust than a fencing. A person or persons could walk or sit on the railing, which would necessitate a higher design load.

I've never heard of anyone designing a fence on a bridge, except on occasion the anchorage.

0.015 ksf? Who knows where it came from, but it seems reasonable. For example, elevator capacity assumes (at least it used to) an average weight per person of 150#. Roughly, there's the 15 psf (body surface area).

 

[bjren]

if 15 psf is the body surface, it will make more sence to apply it on the average people height not the total surface of the fence. when the fence gets higher, 0.015 ksf could create higher load than 0.2+0.05L to its post and anchorage, which doesn't make sence to me.

 

[bridgebuster]

Are you actually designing a chain link fence? If you don't like 15 psf, there's no law saying you can't use a higher number.

 

[MiketheEngineer]

Probably based on wind and maybe some seismic. Probably conservative as chain link lets a lot of air blow thru - but they picked a number to make it easy for everyone??

I've seen plenty of fences on bridges - tends to cut down on suicides and rock throwing..

 

[bjren]

it will make more sense to me if it is wind load. But it is so confusing to put it under the live load section in AASHTO.

 

[bridgebuster]

Generally, wind on a fence is neglected for loads to the substrucutre, unless it's a very dense mesh. Standard chainlink fence - 1" openings - just forget it.

Why does AASHTO do things a certain way? Because they've always done it that way.