Fence Foundation Embedment

[gnault]

I have an 8' tall security fence that is attached to a 4' deep x 1.5' wide continuous concrete pedestal/footing. There is a 2' separation grade between the two sides of the pedestal and the pedestal is embedded 2' on the shallow side. I am trying to determine if the 2' embedment is adequate for wind loading.

I know that there are formulas in IBC for embedment depths of circular posts, but my application is for a continuous footing. Thus, I'm not sure that I can use those formulas.

I also tried looking at the pedestal as a sort of "gravity retaining wall" with a wind load, but the embedment depth required comes out to 4+ feet. This doesn't make much sense compared to a Standard Plan of a Noise Wall that I have which only requires 3'-3" embedment for a similar wall height...and the noise wall is a solid wall whereas my fence is not.

Have any of you had any experience doing something like this? If so, what Code or approach did you use to check for embedment?

Thanks for the help!

 

[FixedEarth]

If you have cohesive soils, you may try a trench footing. Not too long ago, we used to support a 3 story townhouse on 8 inch wide and 48 inch deep trench footing. If you have sandy soils, you may try a grade beam. Foundation design books like Bowles or Peck and Hanson will have the necessary equations.

 

[bridgebuster]

Here's a thought: Take a 2" tall temporary jersey barrier with a fence on it, does anyone ever think about it overturning?

Why not assume a similar condition, that it's free standing? Apply a wind load to the fence, then sum the moments about the base of the foundation. My gut feeling is that it's not going anywhere under normal circumstances.

 

[Ron]

Agree with BB...It usually only takes 10 to 12 inches of embedment to achieve fixity, but you have two considerations to make....the embedment for fixity and the contact stress on the concrete due to the moment at the foundation interface.

One of my clients uses embedded columns for their canopy products. It usually only takes 12 to 14 inches of embedment, but have to check bond for pullout and check contact stress for grout fill and concrete.

 

[msquared48]

Have a couple of beers and it won't be a problem anymore.

I agree with BB and Ron.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[bridgebuster]

Too bad we can't solve all of life's problem with beer. :-(