Chain Link Fence Engineering II 1

[RFreund]

See thread507-388467 for part I. Lots of useful information there.
To follow up on this. I have a few comments / questions in regards to the chain link design guide see here

Quick side note on the spreadsheet in the previous thread
It appears that the spreadsheet uses the full nominal strength of the post without application of a safety factor or reduction factor. The chain link fence guide mentions that the design may see this as fit (I assume because the risk of harm in the event of failure is very low). However, the guide itself applies a 1.5 FoS to the strength of the posts.

Regarding Wind Loads in the guide:
[ol 1]
[li]Does anyone know what Cf (force coefficient) from ASCE7 was used to develop these tables? It appears Cf=1.3 was used based on Table 13.[/li]
[li]Reference is made to the Figure 29.4-1 of ASCE7-10. Technically this would apply for fences that are at least 70% solid (i.e. privacy fences). Is the guide using these pressures then just reducing based on the actual surface area?[/li]
[li]Using Fig 29.4-1 you would also have case A/B and case C to check. It doesn't seem that this is addressed in the guide.[/li]
[li]If your fence is less than 30% open then ASCE7 directs you to Fig 29.5-2 where your Cf is likely to be 1.3 or 1.5 depending on how open your fence is.[/li]
[/ol]

Foundation Discussion
I believe any shallow pier foundation design technique could be use as long as your consistent with identifying your soil properties. There is a fairly popular pole foundation spreadsheet that has 5 options available (LINK). However, I agree that the UBC/IBC method is the most popular and it requires iteration. I believe the guide applies the IBC equation incorrectly in their example. S1 should be the passive resistance at 1/3 the embedment depth. That means they should have used the Lateral soil bearing pressure (LBSP) x 1/3 the trial depth. They also say that the depth is over conservative and just use the minimum based on ASTM F567.
See here:

General question:
Since fences are really not part of a building structure, I don't believe there is any code reference that says ASCE7 needs to be followed so the guide can "pick/choose" whatever sections they'd like to use as applicable. Is there anything wrong with following the guide vs "rigorously" applying ASCE7 as I explained above?
Going along these lines can an owner choose which wind speed to design to? Is there a "standard" wind speed for fences?

EIT

http://www.HowToEngineer.com

 

[kissymoose]

The lack of response is telling.

 

[LOTE]

RFreund,
1. From my analysis, Cf=1.3 was used.
2. I believe this is the case.
3. For a typical fence geometry, only case A is necessary. Any side loading will result in less load, and fence posts are typically circular pole and symmetrical foundation.
4. I am not seeing this. Fig. 29.4-1 allows a reduction factor to be applied when openings are greater than 30%. If they are less than 30%, then no reduction in load.

I agree with you on the 1/3 depth for S1.

Generally, I have seen owners reference ASTM F567 and chain link fence manufactures guides, but not set directly how to design. I think it is up to the designer to make a judgment call based on the soils, threat to the public, risk of the fence fails vs. cost, etc.

My question, for long runs of fencing, do you see a way to increase the post spacing by adding terminal and pull posts? I have a client that keeps pushing back on the spacing proposed and asking if he can add additional terminal posts to decrease the overall spacing.