why are corner fence posts supposed to be bigger than line posts? 1

[KaBone]

I'm sizing the footings and posts based on wind loading. The footing based on overturn moment and the post based on L/120 deflection.
I'm seeing standard details that call for larger posts for gate, corner, end, and pull posts. The gate I can understand if the gate is wider than the post spacing.
The corner and end doesn't make sense to me because it's only carrying half the wind load as a line post, assuming wind loading doesn't occur at 90deg angles.
Am I missing something?

 

[dik]

Line posts have forces acting on them at 180deg and kind of 'balance out'. Corner posts have loads on them from one direction with nothing to help balance them out.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[KaBone]

Can you specify which forces? I looked at dead, live, seismic, rain (no snow), and wind. Wind force far exceeded any of the others.

 

[dik]

Dig up a copy of the CLFMI Manual... it has a lot of really good information.

https://chainlinkinfo.org/clfmi-product-manual-2017-editions/

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[human909]

There are a whole bunch of reasons why larger corners makes sense. Starting from the common sense approach of pin your corners solidly and the rest will stay together.

-Local wind pressures at corners can exceed centre wind forces by a large enough margin that it could make a difference.
-45 degree wind force could result in some high forces especially through tension
-general catenary action tensile forces due to higher than normal allowable deflections results in higher forces on the corners

 

[dik]

and...

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1664593596/tips/Chainlink_Fence_s7uuc2.pdf[/url]

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/raw/upload/v1664593596/tips/Chainlink_Fence_gxzm8l.sm[/url]

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

04, 05, 06, and 07

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Tomfh]

What sort of fence? Are the panels flexural panels?or are they wires/netting?

 

[RontheRedneck]

I have only built farm fences - Barbed wire and high tensile. So my opinion/experience may not be on target for what you're thinking.

Corner posts have uplift forces due to the way they're braced. And horizontal forces from the tension on the wire.

I realize what I'm saying has no bearing on wind loading. But maybe the corner posts are larger for a different reason than wind loading.

 

[dik]

It's the unbalanced tension...

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[BridgeSmith]

human909 touched on the answer - catenary action. With wires or cables that are fairly tight, such as in a fence, wire tension exceeds the lateral load by a large margin.

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

 

[Brad805]

From a construction standpoint you have to tighten the wire or whatever it might be. On the farm, we would tension upwards of 1km of wire. Without braced corner posts that would not be possible.

 

[3DDave]

What kind of fence?

 

[KaBone]

It's a chain link fence.

And big mahalos for all the helpful responses.

 

[3DDave]

Then for certain the tension forces cancel at the mid-posts and are not cancelled at the corners. Tension will be far larger than wind loads if for no other reason to keep the fence from flapping in the breeze.

If this was a solid panel fence which has no tension component then, sure, the corners would be stiffened by the panels and could be the same size as the mid-posts.

 

[kingnero]

Corner posts are more likely to get hit by cars than line posts...

 

[BridgeSmith]

Corner posts are more likely to get hit by cars than line posts...

Probably true, but I doubt that has anything to do with why they're bigger. the effect of a vehicle impact is the pretty much the same for either one.

Corner posts in chain link fences are larger for the same reason utility poles at 'corners' (changes in direction) in power lines, etc. have larger poles and guy wires - the forces on a catenary span are primarily along the span and those forces are balanced for 'line posts', but not for corner posts.

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

 

[kingnero]

Probably true, but I doubt that has anything to do with why they're bigger. the effect of a vehicle impact is the pretty much the same for either one.

When I used to detail pallet racking for a large warehouse, in addition to putting safety bollards, all corner posts were also significantly sturdier for this exact reason. True that the impact is similar, however exposure to incidents goes up exponentially for corner posts. Hence bigger colums. But we're digressing.

 

[BridgeSmith]

Well kingnero, pallet racking is already alot sturdier than posts for chain link, and the typical impact speed in a warehouse would be much lower. For palet racks in a warehouse, I can see that being a worthwhile consideration. However, I maintain that the corner post for chain link fencing is not enough sturdier than a line post to matter a bit when it gets hit by a car, and I'm fairly sure that's not a consideration in sizing the posts.

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