Fence Pole Embedded in Concrete

[onealexis]

Ok, this is my first post, I'm a liiittle nervous!

Can anyone please point me in the direction of 'how to' or a reference for the following -

I have a fence on top of a concrete wall. We calculated the required Sx of the post based on the wind, etc. Now we have to determine the post embedment into the 12" wide concrete wall.

We do not know at this time the reinforcement in the wall as that is being done by another party. Since the moment is not all that large (about 15 ft.k) I thought the first thing I would do is simply determine if the shear strength of the concrete alone would be sufficient.

I tried using the Vc formula from Chap. 11 (11.3.1.1) if I remember correctly, but it rendered a very high shear strength.

So, I decided to go to Appendix D, but each time I attempt to calculate the break-out strength I get frustrated because it so often references "headed anchor studs" or it seems the 4.5" dia. pole I have coupled with the embedment throw the formula and the results off.

Is there another formula or method I should be employing?

Thanks!

 

[ash060]

I would check the moment capacity of the wall using the effective width as defined by PCI. In this case it would probably be 6x the wall thickness or 0.4x wall height.

Sx also is not a function of the load, but will be used to calculate the stress in the post. Make sure to not exceed allowable stress for the material.

Appendix D can be used in your case, but also check bearing of your materials. Your le will equal hef in your case but because your anchor is so large I might not measure ca from the center of the post, but from the face of the post to be conservative.

 

[bridgebuster]

It would be much easier from a construction standpoint to use a baseplate on the post and then anchor it to the wall.

 

[Ron]

I believe your question is how much embedment is needed for the post (to achieve fixity and not exceed the concrete strength).

Use the projected area of the post and consider that the force from your moment couple will not crush the concrete at the top of the concrete, and that the tension in the concrete created by the force will not exceed the concrete strength (with or without reinforcement, depending on your condition). Use an embedment length that will satify the reduction in couple force necessary to satisfy both conditions. Please note that the tension consideration will likely prevail as you will not likely be able to get enough compression at the post wall to make any difference.

 

[sandman21]

Appendix D is based on test for anchors with less than 25" of embed and an anchor less than 2" dia. don’t think the equations would really predict the case of an embedded pole.

 

[onealexis]

That's exactly what we've been finding Sandman...