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Re: Anchor Bolt Shear in Round Pier

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Jake,

Thanks for your response.  Let me ask some add'l questions.

I have a concrete breakout issue because it is a round pier.  No matter
what direction the load is in it wants to break out to the pier at a free
edge.

This "hairpin" is a little confusing without a sketch.  Would it be best
to consider a rectangular tie that would enclose each bolt at a 90 degree
bend?  I'm not sure how I would calculate the required area of steel for
this.

What puzzles me is I know the round pier can take this shear with ties,
it's just the PCA method has the "breakout" shear model can't get the
force from the bolts to the concrete without failure of the concrete.

Rich



On Mon, 20 Sep 2004 19:56:34 -0600 "Jake Watson" <jwatson(--nospam--at)utahisp.com>
writes:
> 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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