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# RE: Anchor Bolt Shear in Round Pier

• To: <seaint(--nospam--at)seaint.org>
• Subject: RE: Anchor Bolt Shear in Round Pier
• From: "Jake Watson" <jwatson(--nospam--at)utahisp.com>
• Date: Mon, 20 Sep 2004 19:56:34 -0600

```ACI 318 Appendix D basically assumes that the concrete is unreinforced.  If
you add reinforcing and detail it to transfer your loads, you will be okay.
For example, if you have a concrete breakout issue, develop enough of a tie
inside the cone for your force.  The trick is to develop the tie across the
plane of the shear cone.  Once the force is into the main pier, you treat it
just like any other force.

I will try to spell out a better example, but it will be a little hard
without a drawing.  If your shear force is perpendicular & away from a free
edge, you will likely have breakout problems like you mentioned.  Provide a
"hairpin" or similar tie around each bolt or the bolt group.  Extend the
hairpin back into the main body of concrete and detail the rebar using rebar
development equations.  Watch the development length on each side of the
shearcone.

HTH,

Jake Watson, P.E.
Salt Lake City, UT

-----Original Message-----
From: richard lewis [mailto:rlewistx(--nospam--at)juno.com]
Sent: Monday, September 20, 2004 6:33 PM
To: seaint(--nospam--at)seaint.org
Subject: Anchor Bolt Shear in Round Pier

There was a little discussion of this last week regarding the IBC tables
in chapter 19, but I don't think it addresses my question so I am sending
a new question for comments.

I am designing an anchorage for a steel column on a round concrete pier.
The column is a W14X61.  The pier is tentatively set at 24" diameter.  I
located the 4 anchor bolts inside the column flanges, basically on a 8" x
9" rectangle.

I have a factored shear load of 22.4 kips and no uplift.  I was looking
at the PCA anchor bolt method of design, which is the same as the ACI
code and I believe section 1613 of the IBC.  The maximum shear value I
was getting was just under 8 kips for concrete breakout.  I was wondering
if there was a design procedure where I could have closely spaced column
ties to bound the concrete core and prevent the concrete breakout.  Is
there such?  If so. what is it?  The PCA method does allow the PSI7 value
to be slightly increased for having reinforcing between the bolt and the
edge, but it really is not much.

Thanks for your help.

Rich

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