Qualification of Post-Installed Adhesive Anchors in Concrete (ACI 355.4M-11) and Commentary
|Publication Date:||1 September 2011|
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 318M 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 6 mm or larger. The drilled hole shall be approximately cylindrical with a diameter do less-than or equal to 1.5da. This standard also applies to anchors with an anchor embedment depth hef not less than four diameters (4da), or 41 mm, and an embedment depth not exceeding 20da.
The minimum diameter of 6 mm 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 318M, Appendix D, is based on an analysis of an anchor database with a maximum diameter of 50.8 mm. While ACI 355.4M 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 38 mm.
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 318M, Appendix D.