Beginning with the 2003 International Building Code, building codes directly address the design and use of post-installed mechanical anchors in concrete. This code references ACI 318 Building Code Requirements for Structural Concrete, which includes Appendix D-Anchoring to Concrete.

Appendix D provides a strength design methodology to calculate nominal tension and shear strength values for post-installed mechanical anchors used in cracked or uncracked concrete. This differs from the more "traditional" allowable stress design methodology that considers use of post-installed mechanical or adhesive anchors in uncracked concrete only and has been used to develop the allowable load values for the other products featured in this catalog. In the case of the strength design methodology, the designer calculates the nominal strength of an anchor or group of anchors in cracked or uncracked concrete (as applicable), considering each possible failure mode (see Table 1). The "controlling" design strength value is the lowest calculated design strength value considering each of the possible failure modes.

Note that Appendix D is limited in scope. Presently, it covers structural anchors (both cast-in anchors and some types of post-installed mechanical anchors) related to strength, stability or life-safety. These anchor types may be installed and used in normal-weight or lightweight aggregate concrete.Other base materials, such as masonry, are not covered. Only those post-installed mechanical anchors which have been tested and evaluated in accordance with ACI 355.2 Evaluating the Performance of Post-Installed Anchors in Concrete may be considered. Other anchor types, such as concrete screws and adhesive anchors are not yet included within the scope of ACI 318, Appendix D or ACI 355.2. Additional limitations based on maximum concrete compressive strength, maximum anchor diameter and maximum embedment depth must also be considered.

Table 1 - Possible Failure Modes for
Post-Installed Mechanical Anchors in Concrete

In order to use the design provisions of ACI 318, Appendix D, post-installed mechanical anchors must be tested and qualified under ACI 355.2 Evaluating the Performance of Post-Installed Anchors in Concrete. The results of these tests are used to establish such performance values as the effectiveness factor, pullout resistance, axial stiffness, and anchor category. The anchor category is established based on the reliability of an anchor's performance during testing and is particularly important as it is used to determine the appropriate strength reduction factor.

The performance of post-installed mechanical anchors for use in either uncracked or in both cracked and uncracked concrete can be established under ACI 355.2. In order to qualify a product for use in both cracked and uncracked concrete, and under seismic loading conditions, a series of thirteen separate tests must be conducted. These tests include:

• Tension testing in low and high strength concrete where the anchor has been installed in a 0.012-inch wide crack.
• Tension testing in low strength concrete where the anchor is installed in a crack that is cycled 1,000 times between a width of 0.004 and 0.012 inches while simultaneously being subjected to a sustained tension load.
• Tension and shear testing in low strength concrete where the anchor is installed in a 0.020-inch wide crack and subject to a simulated seismic tension or shear load that varies in magnitude over 140 load cycles.

ICC Evaluation Services AC 193 references ACI 355.2 and details additional requirements pertaining to product sampling and testing.