Timber post foundation problem 1

[SchoolnStuff]

I am attaching a drawing I made I have a timber post 5" x 6 7/8". I am trying to determine the depth into a circular steel sheeting that will be filled up with concrete to act as our pile. I have found the moments acting in the x (3520 ft-lbs) and z axis (3520 ft-lbs) and from there calculated the resultant moment (4978 ft-lbs). I am in Florida but I don't have a geotech report to get soil conditions so I will use the Florida standard 50 pcf unit weight and N-blowcount of 15. I am just looking for some guidance as to how I can continue from here.

 

[HTURKAK]

Pls look IBC 2012 ,Section 1807.3 Embedded Posts and Poles. You can use the formula 18-1 to determine the embedment depth.

You may search the forum for ( pole , post foundation) .One of the outcomes ;

thread507-515166






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[SchoolnStuff]

I have seen this formula before but will this help me if I am trying to find the depth of the post IN a concrete foundation?

 

[phamENG]

It's not altogether straightforward. You need to draw a free body diagram of your post, but rather than just calling the base 'fixed' you need to drill down and look at how it's interacting with the foundation. It will be embedded, so you'll be forming a force couple within the concrete to resist the moment. For simplicity's sake, you could put one reaction at the top surface of the concrete and then see how far down the other needs to be to keep shear in the post within limits. But this ignores crushing. For that, you'll need a distributed load. For wood on concrete, I prefer a triangular distribution. So it'll look a bit like a pile under lateral load diagram.

After that, you need to make sure the concrete won't fail in shear. With a wood post you're probably safe. Gets a little harder when you have a small steel member. Search for embedded guardrail post or pocket detail on the site and you'll find some good, in depth discussions on it.