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RE: Anchorage to concrete

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I have a different question on anchor bolt embedment: In Table 19-D (UBC97),
what does "minimum embedment" refer to and where is it defined?  And what
does footnote 1 mean when it states "Bolts shall have a standard head or an
equal deformity in the embedded portion."  

I have an equipment manufacturer claiming their hooked anchor bolts meet
this UBC table, measuring embedment from the concrete surface to the bottom
of the hooked bolt.  I've accepted the hooked bolt (although it is not clear
that it is "an equal deformity") but I suggested that the embedment depth
should be measured to the bearing surface, i.e. the top surface of the
hooked portion.  The manufacturer says "prove it" per the code. 

> -----Original Message-----
> From: Tom.Hunt(--nospam--at)fluor.com [mailto:Tom.Hunt(--nospam--at)fluor.com]
> Sent: Wednesday, November 10, 1999 10:34 AM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Anchorage to concrete
> 
> 
> 
> 
> Randy,
> 
> As a general comment, the analysis and failure modes for a 
> hooked anchor are
> significantly different then for a headed anchor.  A headed 
> anchor will develop
> the traditional pull out cone, however, a hooked anchor will 
> fail by crushing of
> the concrete in the hook area, splitting in the plane of the hook, or
> unacceptable slip at the concrete surface.  AISC Steel Design 
> Guide Series on
> "Column Base Plates" has some simplified formulas and for a 
> detailed analysis
> and stress concentration profile see Park and Paulay 
> "Reinforced Concrete
> Structures"
> 
> Thomas Hunt, S.E.
> Fluor Daniel
> 
> 
> 
> 
> 
> "Randy Hamilton P.E." <rh-eng(--nospam--at)dakotacom.net> on 11/08/99 10:03:34 PM
> 
> Please respond to seaint(--nospam--at)seaint.org
> 
> To:   "Seaint" <seaint(--nospam--at)seaint.org>
> cc:    (bcc: Tom Hunt/AV/FD/FluorCorp)
> 
> Subject:  Anchorage to concrete
> 
> 
> 
> Can anyone lead me to a source to prove that a hooked anchor 
> bolt (j-bolt)
> can develop the loads typically used for hold downs when cast 
> into a stem
> wall.
> 
> Using section 1925.3.2 ('94 UBC) with a phi factor of .85 
> (assuming the
> j-bolt is hooks around a horizontal bar) and an edge distance 
> of 2.75 inches
> (assuming an 8 inch stem wall but the bolt is centered in a 
> 5-1/2 inch 2x6
> plate), what should the value be for As?
> 
> If I use concervatively a truncated cone with a diameter of 
> 5.5 inches and
> an embedment length of 2.75" so as not to have to reduce for 
> lack of edge
> distance, I come up with a tension value of 4045# for 2500 
> psi concrete.
> For service load design, this would need to be reduced by a 
> load factor of
> 1.3 for wind and 2.0 for no special inspection which results 
> in a value of
> 1555#.  This does not develop the load for even an HD2A 
> bolted to a double
> stud.
> 
> I assume it is acceptable to use more surface area then this 
> conservative
> assumption but the question is how much and how is it justified?
> 
> Thanks in advance for any input.
> 
> Randy Hamilton P.E.
> Tucson, AZ
> 
> 
> 
> 
> 
> 
> 
>