Maximum Working Load
The maximum safe working load should not exceed 1/4 of the average ultimate values of a specific anchor size. A higher safety factor may be required for applications with cyclic, fatigue or shock loads and should be selected by the designer on that basis.
For each type of anchor, a minimum depth of embedment is specified. This is minimum depth for an anchor to be installed and still meet minimum pullout values. Anchors installed less than minimum depth will stress the base material above its limits and may cause failure during installation or expansion of the anchor. Embedment depth is a critical factor in determining load capacity of an anchor, and it represents the point at which the anchor’s expansion forces are acting on the concrete. The required anchor embedment is the distance from the concrete surface to the bottom of the anchor.
Minimum Anchor Spacing
For each type of anchor, a spacing distance between anchors is specified. The load bearing capacity of an anchor is influenced by an adjacent anchor. Anchor spacing is the minimum distance between two anchor center lines without an influence on the tensile or shear failure load of either anchor. Generally, a spacing of 10 diameters between anchors is appropriate. For wedge and sleeve anchors, the spacing distance may be reduced by 50% provided the shear and tension values are reduced by 40%. For drop in anchors, the spacing distance may be reduced by 50%, provided the shear and tension values are reduced by 50%. Linear interpolation may be used for intermediate spacings. Spacing reduction factors are cumulative for groups of three or more anchors.
Minimum Edge Distance
For each type of anchor, a minimum edge distance is specified. Due to reduced material volume, a minimum edge distance must be maintained to prevent the edge from breaking away prematurely when the anchor is installed. Also, a safe edge distance must be maintained in order to achieve the full load bearing capacity of the anchor. A minimum edge distance of 5 diameters is recommended. Drop in anchors should have a minimum edge distance of 8 diameters. For wedge and sleeve anchors, the edge distance may be reduced by 50%, provided the shear and tension values are reduced by 40%. For drop in anchors, the spacing distance may be reduced by 50%, provided the shear and tension values are reduced by 50%.
Anchors loaded in tension and shear simultaneously, will generally have ultimate capacities lower than an anchor loaded in tension and shear separately. Combined loads should be calculated on a straight line interaction diagram of pure shear (S) and pure tension (T).
S APPLIED T APPLIED
S ALLOWED + T ALLOWED Less than or equal to 1