4.0 INFLUENCE OF HOLLOW HEAD JOINTS ON CMU DESIGN
For CMU construction with hollow head joints , in addition to the ends and edges of walls , the nearest head joint on a horizontal projection from the anchor shall be treated as an edge for design purposes . The minimum distance from the nearest adjacent hollow head joint as measured from the centerline of the hollow head joint in CMU construction shall be 2 inches for adhesive anchors or the c min , HJ value for mechanical anchors , which is provided in the product installation information tables .
The following illustrations will demonstrate how to locate the nearest adjacent head joint and how treating it as an edge will affect calculating tension breakout cones for single anchor , two anchor , and four anchor configurations . Additionally , the illustrations will demonstrate anchors installed in the face of the same CMU block , in the face of different CMU blocks ( horizontally or vertically adjacent ), and in the bed joints .
The following illustrations , based on the masonry anchor design provisions of ICC-ES AC01 and AC58 , are intended for illustration purposes only .
Face of CMU — Single Anchor and Horizontal Groups
Figure 2 — Examples of Breakout Cones for Single Anchor and Horizontal Groups
Anchors A and B in Figure 1 represent single anchor installations . They illustrate which head joint would be considered the nearest adjacent head joint edge ( C hj
) for the respective anchor . Cone A in Figure 2 illustrates the tension breakout cone for Anchor A considering the influence of the nearest adjacent head joint edge as well as the top of wall edge .
Anchors C and D in Figure 1 represent a two-anchor configuration . They illustrate which head joint would be considered the nearest adjacent head joint edge when installed in the same CMU block . Cone CD in Figure 2 illustrates the tension breakout cone for Anchors C and D considering the influence of the nearest adjacent head joint edge .
Anchors E and F in Figure 1 represent a two-anchor configuration . They illustrate which head joint would be considered the nearest adjacent head joint edge when two anchors are installed in different horizontally adjacent CMU blocks and do not share the nearest adjacent head joint edge .
Figure 1 — Examples of Nearest Adjacent Head Joint for Single Anchor and Horizontal Groups
Anchors G and H in Figure 1 represent a two-anchor configuration . They illustrate which head joint would be considered the nearest adjacent head joint edge when two anchors are installed in different horizontally adjacent CMU blocks and do share the nearest adjacent head joint edge . Cone GH in Figure 2 illustrates the tension breakout cone for Anchors G and H considering the influence of the nearest adjacent head joint edge as well as the bottom of wall edge .
8 Masonry Fastening Technical Guide Edition 24 Hilti , Inc . 1-800-879-8000 | en español 1-800-879-5000 | www . hilti . com | Hilti ( Canada ) Corporation | www . hilti . ca | 1-800-363-4458