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Foundation A.B. Capacity

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Jake,

With extreme loads in narrow stem walls like you are experiencing, forget 
about the shear cone resistance.  Extend the A.B. down into the footing, put 
a plate on it and engage longitudinal reinforcing in the footing.  Just make 
sure that you have enough weight of concrete (footing and stem wall) and soil 
overburden to resist the uplift that you have by 50 percent.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Jake Watson wrote:

>>I am trying to find the capacity of an anchor bolt in a residential
foundation wall.  The case has a large uplift do to a "Simpson" holdown
(about 15k service loading). It is a traditional 8" foundation wall with
a simpson HD15 anchor that requires a 1.25" dia anchor bolt.  Simpson
doesn't make a corresponding SSTB.  I tried to design an anchor bolt
using the provisions of ch19, div III but am very confused.  According
to the provisions, I first calculate the projected area area at the top
of the wall (Ap) then reduce according to edge distance.  The reduction
amounts to edge distance divided by embedment length.  I have two close
edges (4") so I squared the reduction.  After doing all this, the UBC is
trying to tell me that a 30" long A.B. is weaker than a 12" long A.B. 
If someone could clarify these provisions, I would be very grateful.

P.S. Here's the fun part, if I design it at as a rebar, then I have more
than 10x the capacity of an A.B.

Suggestions?

Thanks in advance, 
        Jake Watson, E.I.T
        Salt Lake City, UT<<