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Re: Flag-Pole Foundations for light framing

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Hi,
According to ANSI?NAAMM FP1001-97, there would be no reinforcement to be placed in the 30" sqx 48"
deep ftg.If you treat as an isolated ftg. with four anchor bolts, in my opinion, there should be a
minimum reif. per ACI 318-02. i.e. 0.005 x gross area.


>>> dennis.wish(--nospam--at)verizon.net 11/19/2003 4:02:37 PM >>>
I have two Flag-pole foundations designed for the front of a custom home
where the forces in each column (lateral force) based on an R of 2.2 is
690-pounds placed at 12'-0" above the top of the foundation. The entry
is flatwork which is monolithically placed and is, in my opinion,
sufficient to restrain the top of the column. A 18-inch square
foundation pier extends up from the flatwork six inches and the
foundation is 4'-0" below soil and 30" square. The Column is a TS
6x6x5/16" square tube has approximately 6-inches of flatwork on the two
exposed edges of the flatwork (outside edges) and is continuous between
columns.

 

The plan check corrections asked for two things:

 

1.	The minimum reinforcement for the concrete foundation 
2.	The clearance surrounding the columns to show adequate restraint
of the flatwork. It is assumed that the area in front of the columns
will also be done in either brick/tile or concrete sidewalks with an
area abutting the entry flatwork.

 

Unless the lateral loads were large, I have not in the past provided
reinforcement with this much cover around the steel columns. The columns
extend through the foundation and are secured to a 12" thick erection
pad. The column should be sufficient to handle the moment in the base,
and the concrete transfer the bending moment below grade without the
need of a cage or vertical rebar. The passive soil pressure should also
be sufficient due to the analysis to resist overturning of the columns
with such low lateral loading. The erection pad is more than sufficient
to support the entry roof dead and live loads.

Am I missing something here? Is there a minimum steel requirement for a
flagpole with small lateral loads? Where would I find the information in
the 97 UBC that might reference ACI-318 on this issue?

 

I have always used flatwork as a means to offer restraint against
rotation of small lateral load columns. What, if any, is the minimum
edge requirements to the edge of the foundation especially since the
piers extend above a post hole foundation that is 30-inches square and
48" deep?

 

TIA

 

Dennis S. Wish P.E.


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