Using strength design, compute the design shear capacity of a 1/2-in. diameter, A307 bent-bar anchor with a 1-in. hook, embedded horizontally in a grouted cell of a nominal 8-in. wall with a specified compressive strength, f ² m, of 1500 lb/in.2. Assume that the bottom of the anchor hook is embedded a distance of 4.5 in., and that the anchor is located far from free edges in the direction of applied shear. This might represent an anchor used to attach a ledger to a masonry wall. Because free edges are not a factor, shear breakout does not apply. First, compute the effective embedment, lb. In accordance with Sec. 1.16.5 of the 2008 MSJC Code, this is equal to the total embedment of 4.5 in., minus the diameter of the anchor (to get to the inside of the hook), and minus an additional anchor diameter, or 3.5 in. The projected tensile breakout area has a radius of 3.5 in. (diameter of 7 in.).
Now obtain the design capacity by multiplying the nominal capacity by the corresponding strength-reduction factor from Sec. 3.1.4.4 of the 2008 MSJC Code:
Now obtain the design capacity by multiplying the nominal capacity by the corresponding strength-reduction factor from Sec. 3.1.4.4 of the 2008 MSJC Code:
φBvns = 0.9 ⋅ 5400 lb 2008 MSJC Code, Sec. 3.1.4.4
φB vns = 4860lb
The governing design shear capacity is the lowest of that governed by masonry crushing (2033 lb), pryout (5962 lb), and yield of the anchor shank (4860 lb). Because the anchor is not close to a free edge, shear breakout does not apply. Masonry crushing governs, and the design shear capacity is 2033 lb.
If this problem had involved an anchor loaded toward a free edge, then shear breakout would have had to be checked.
