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# Deep Embedded HSA tension capacities in CMU

• To: <seaint(--nospam--at)seaint.org>
• Subject: Deep Embedded HSA tension capacities in CMU
• From: utej(--nospam--at)attbi.com
• Date: Wed, 11 Sep 2002 19:51:59 +0000

```The 1997 UBC masonry chapter 21 and ACI 530 Masonry
Specification give equations to calculate the allowable
tension load capacities in a masonry wall.  One equation
is to determine the masonry wall resistance capacity
(Bt=0.5*Ap*(fm)^0.5) and the other equation is to
determine the anchor bolt resistance capacity
(Bt=0.2*Ab*fy).  The Ap in the first equation is the
projected area calculated using the lesser of (1) the
anchor embedment depth as the radius in the pi*r^2
equation and (2) the anchor edge distance as the radius
in the same equation.  Therefore, if one had a anchor
bolt in the top of a 8" nominal width masonry wall, one
would have a 3.81" edge distance and be limited to
Ap=3.81^2*pi.  Therefore, the code and specification do
not seem to take into account additional resistance
capacity provided when deeper embedments are provided.
In the anchor in the top and middle of the masonry wall,
it appears that one could reasonably determine Ap based
on the area of the projected cone on the masonry surface
for deeper embedments.  In this case, it would closely
resemble a rectangle and the Ap equation would be Ap =
(Embedment Depth * 2) + (Edge Distance * 2).

In addition, the code and specification Bt equation to
determine the steel resistance capacity is less than
shown by the AISC Manual of Steel Construction.  The
reasoning for this is stated in the ACI 530
Specification Commentary section 2.1.4.2.2 as
follows "Bent bar anchors often failed by completely
sliding out of the specimen."  Therefore, the reduced
steel anchor bolt tension resistance capability.
However, if one uses headed stud anchors, should not an
increased steel bolt tension resistance capability be
obtained?

Have these questions been addressed in any committees,
codes, or standards?

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