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RE: embed bolts in CMU

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Footnote #1 states that values are for bolts having a standard head or an
equal deformity (whatever that means).

Tom Hammond

> -----Original Message-----
> From: utej(--nospam--at)attbi.com [mailto:utej(--nospam--at)attbi.com]
> Sent: Monday, September 16, 2002 4:15 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: embed bolts in CMU
>
>
> Upon further review of ACI 530-02 (which is adopted with
> additional requirements by the IBC) strength design
> provisions, they have differentiated between the tension
> capacity of a headed stud anchor and a bent bar anchor
> in masonry.  Headed stud anchor are designed for the
> lesser of the masonry capacity (Ban = 4*Apt*(f'm)^0.5)
> and the steel capacity (Ban = Ab*Fy).  Bent-bar anchors
> use the same two equations and add a third equation for
> the strength governed by anchor pullout (Eq. 3-6).
>
> In the ACI 530-02 commentary section 3.1.6.2, it
> states "The tensile strength of a bent-bar A.B. is
> governed by yield and fracture of the anchor steel, by
> tensile cone breakout of the masonry, or by
> straightening and pullout of the anchor from the
> masonry.  Capacities corresponding to the first two
> failure modes are calculated as for headed stud anchors."
>
> In addition, ACI 530-02 section 3.1.6.1.1 states that
> one is to calculate the projected area with the
> following equation: Ap = pi*embedment depth^2
> (Ap=pi*Lb).  Then it goes on to state that "The portion
> of the projected area overlapping an open cell, open
> head joint, or that is outside the wall shall be
> deducted from the value of Apt.."
>
> Therefore, ACI 530-02 and the IBC have addressed (1) the
> anchor bolt tension capacity (greater if one uses a
> headed stud anchor) and (2) it allows increased capacity
> for deeper embedments as long as reductions in edge
> distances are taken.
>
> With this being said, does anyone know if Table 19-D,
> regarding "Allowable Service Load on Embedded Bolts"
> (which has been in the UBC since the early 70's) in the
> 1997 UBC and as Table 1912.2 in the IBC, allowable
> embedded bolt in concrete load values are based upon
> bent-bar anchors?  Most likely they are and, therefore,
> headed stud anchors, or any anchor other than bent-bar
> anchors, would receive an unwarranted penalty when
> designed using this table.
>
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