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Description / Abstract:
This standard applies only to post-installed adhesive anchors as
defined herein.
Adhesive anchors resist tension loads with a combination of
adhesion and mechanical bond (micro-interlock). Different anchor
designs and adhesive types may exhibit a range of performance
characteristics. In particular, the sensitivity of adhesive anchors
to variations in installation and service-condition parameters
(such as hole cleaning, installation orientation, and cracked
concrete characteristics) may vary widely from each system. ACI 318
addresses this situation by matching capacity reduction factors to
anchor performance categories that are, in turn, established
through a series of reliability tests.
This standard applies to anchors with a diameter
da of 1/4 in. or larger. The drilled hole shall
be approximately cylindrical with a diameter do
≤ 1.5 da. This standard also applies to anchors
with an anchor embedment depth hef not less than four diameters
(4da), or 1-5/8 in., and an embedment depth not
exceeding 20da.
The minimum diameter of 1/4 in. is based on practical
considerations regarding the limit of structural anchor
applications. The upper limit on the ratio of hole diameter to
anchor element diameter provides a demarcation between conditions
where a single bond strength can be used to evaluate anchor
strength and conditions where bond strengths at both the anchor
interface and concrete interface must be determined to evaluate
anchor strength. In addition, the value of 1.5da is based on
consideration of typical practice whereby most organic adhesives
are used with thin bond lines to limit both adhesive shrinkage and
creep of the anchor when under load. The design method deemed to
satisfy the anchor design requirements of ACI 318, AppendixD, is
based on an analysis of an anchor database with a maximum diameter
of 2 in. While ACI 355.4 gives no limitations on maximum anchor
diameter, for anchors beyond this dimension, the testing authority
should decide if the tests described in this standard are
applicable or if alternative tests and analyses are more
appropriate. It may also be desirable to reconsider those tests
where only small, medium, and large diameters are tested when the
upper diameter is much larger than 1-1/2 in.
A limitation on the minimum embedment length of adhesive
anchors is necessary to ensure conformance with the design method
deemed to satisfy the anchor design requirements of ACI 318,
Appendix D.
The minimum member thickness shall not be less than the value
given by Eq. (10-21). Values of Δh in Eq. (10-21) shall be
permitted if they are verified by tests according to Table 3.1,
Test no. 14, and Table 3.2, Test no. 20, or Table 3.3, Test no.
15.