Masonry Magazine August 1987 Page. 28
When anchors are located less than 12 anchor diameters from a free edge, the allowable shear load is determined by linear interpolation from a value of VA obtained in Eq. 5 at an edge distance of 12 anchor diameters to an assumed value of zero at an edge distance of 1 in. (25 mm). This takes into consideration the reduction in the masonry shear capacity due to the edge distance.
Combined Tension and Shear
Allowable combinations of tensile and shear loads are based on a linear interaction equation between the allowable pure tension and pure shear loads calculated in Eqs. 1, 2, 5 and 6. Anchors subjected to combinations of tension and shear are designed to satisfy the following equation:
T/TA+V/VA 1.0
(Eq. 7)
where:
T Applied tensile load, lb.,
V Applied shear load, lb.
Proprietary Anchor Bolts
The allowable load equations previously presented are intended for use with plate anchors, headed bolts and bent bar anchors and have been proposed to the ACI/ASCE 530 Committee on Masonry Structures. However, when the allowables from these equations are compared to test results for proprietary anchors, they appear to produce acceptable safety factors.
Allowable Loads. Average factors of safety are 4.0 for tensile tests and 5.0 for shear tests on proprietary anchors. The combined tension/shear interaction equation produced an average safety factor of 7.0 when compared to test results on proprietary anchors. Therefore, based on comparison to test results, the allowable load equations proposed in this Technical Notes are suggested for use in the design of proprietary anchors in brick masonry. The embedment depth used to calculate the allowable load values should be equal to the embedded depth of the proprietary anchor.
Edge Distance. Edge distance is of particular concern when expansion anchors are used in brick masonry, due to lateral expansion forces produced when the anchors are tightened. These forces are often large enough to cause
TABLE 3
Allowable Shear on Bolts and Anchors*¹
| Bolt or Anchor Diameter, In. | Minimum² Embedment, In. | Allowable Shear Load, Lb |
|---|---|---|
| | | Without³ Inspection | With⁴ Inspection |
| 1/4 | 4 | 180 | 270 |
| 3/8 | 4 | 270 | 410 |
| 1/2 | 4 | 370 | 550 |
| 5/8 | 4 | 500 | 750 |
| 3/4 | 5 | 730 | 1,100 |
| 7/8 | 6 | 1,000 | 1,500 |
| 1 | 7 | 1,230 | 1,850 |
| 1-1/8 | 8 | 1,500 | 2,250 |
*¹From Building Code Requirements for Engineered Brick Masonry, Brick
Institute of America, August 1969.
¹In determining the stresses on brick masonry, the eccentricity due to loaded bolts and anchors shall be considered.
²Bolts and anchors shall be solidly embedded in mortar or grout.
³No engineering or architectural inspection of construction and workmanship.
⁴Construction and workmanship inspected by engineer, architect or competent representative.
TABLE 4
Allowable Shear on Anchor Bolts From UBC
1985 Edition"
(a) ALLOWABLE SHEAR ON ANCHOR BOLTS
FOR CLAY AND CONCRETE MASONRY
| Diameter (inches) | Total Embedment² (inches) | Allowable Shear³ (lbs) |
|---|---|---|
| 1/4 | 4 | 270 |
| 3/8 | 4 | 410 |
| 1/2 | 4 | 550 |
| 5/8 | 4 | 750 |
| 3/4 | 5 | 1100 |
| 7/8 | 6 | 1500 |
| 1 | 7 | 1850⁴ |
| 1-1/8 | 8 | 2250⁴ |
¹An anchor bolt is a bolt that has a right angle extension of at least three diameters. A standard machine bolt is acceptable.
²Of the total required embedment, a minimum of five bolt diameters must be perpendicular to the masonry surface.
³No reduction in values required for uninspected masonry.
⁴Applicable for units having a net area strength of 2500 psi or more.
(b) ALLOWABLE SHEAR ON BOLTS FOR EMPIRICALLY
DESIGNED MASONRY EXCEPT UNBURNED
CLAY UNITS
| Diameter Bolt (inches) | Embedment¹ (inches) | Solid Masonry (Shear in Pounds) | Grouted Masonry (Shear in Pounds) |
|---|---|---|---|
| 1/2 | 4 | 350 | 550 |
| 5/8 | 4 | 500 | 750 |
| 3/4 | 5 | 750 | 1100 |
| 7/8 | 6 | 1000 | 1500 |
| 1 | 7 | 1250 | 1850² |
| 1-1/8 | 8 | 1500 | 2250² |
¹An additional 2 inches of embedment shall be provided for anchor bolts located in the top of columns for buildings located in Seismic Zones Nos. 2, 3, and 4.
²Permitted only with not less than 2500 pounds per sq in. units.
*"Reproduced from the Uniform Building Code, 1985 Edition, Copyright 1985 with permission of the publisher, The International Conference of Building Officials."