17.4.5 Bond Strength of Adhesive Anchor in Tension
(a) For a single adhesive anchor:
Factors ψec,Na, ψed,Na, and ψcp,Na are defined in 220.127.116.11, 18.104.22.168, and 22.214.171.124, respectively. ANa is the projected influence area of a single adhesive anchor or group of adhesive anchors that shall be approximated as a rectilinear area that projects outward a distance cNa from the centerline of the adhesive anchor, or in the case of a group of adhesive anchors, from a line through a row of adjacent adhesive anchors. ANa shall not exceed nANao, where n is the number of adhesive anchors in the group that resist tension loads. ANao is the projected influence area of a single adhesive anchor with an edge distance equal to or greater than cNa:
|ANao = (2cNa)2||(126.96.36.199c)|
and constant 1100 carries the unit of lb/in.2
The characteristic bond stress τcr shall be taken as the 5 percent fractile of results of tests performed and evaluated according to ACI 355.4.
For adhesive anchors located in a region of a concrete member where analysis indicates no cracking at service load levels, τuncr shall be permitted to be used in place of τcr in Eq. (188.8.131.52) and shall be taken as the 5 percent fractile of results of tests performed and evaluated according to ACI 355.4.
It shall be permitted to use the minimum characteristic bond stress values in Table 184.108.40.206, provided (a) through (e) are satisfied:
(a) Anchors shall meet the requirements of ACI 355.4
(b) Anchors shall be installed in holes drilled with a rotary impact drill or rock drill
Table 220.127.116.11—Minimum characteristic bond stresses
|Installation and service environment||Moisture content of concrete at time of anchor installation||Peak in-service temperature of concrete, °F||τcr, psi||τuncr, psi|
|Outdoor||Dry to fully saturated||175||200||650|
Where anchor design includes sustained tension loading, multiply values of τcr and τuncr by 0.4.
but ψec,Na shall not be taken greater than 1.0.
If the loading on an adhesive anchor group is such that only some adhesive anchors are in tension, only those adhesive anchors that are in tension shall be considered when determining the eccentricity e'N for use in Eq. (18.104.22.168) and for the calculation of Nag according to Eq. (22.214.171.124b).
In the case where eccentric loading exists about two orthogonal axes, the modification factor ψec,Na shall be calculated for each axis individually and the product of these factors used as ψec,Na in Eq. (126.96.36.199b).
|If Ca,min ≥ Cac, then ψcp,Na = 1.0||(188.8.131.52a)|
|If Ca,min < Cac, then||(184.108.40.206b)|