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Re: embed bolts in CMU

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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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