Guide to the Concrete Capacity Design (CCD) Method—Embedment Design Examples

Description

This report was prepared by the members of the ACI 349Subcommittee on Steel Embedments to provide examples of the application of ACI 349 to the design of steel embedments. The first edition of this report, published in 1997, was based on ACI 349-97 that used the 45-degree cone breakout model for determining the concrete breakout strength.

The 2001edition of the Code* marked a major departure from the previous editions with the adoption of the concrete capacity design (CCD) method. The model for the concrete breakout strength used in the CCD method is a breakout prism having an angle of approximately 35 degrees. In addition, theconcrete breakout strength for a single anchor away from theedge is proportional to the embedment depth raised to the power of 1.5 and not embedment depth squared, as used inthe previous versions of the Code. These and other changes in the Code result in designs that are somewhat different thanthose obtained using previous editions of the Code.

The examples used in this report are based on the ACI 349-06,Appendix D, and illustrate how the CCD method is applied.In previous editions of ACI 349, the anchorage design was given in Appendix B. Because ACI 349 is a dependent code, the chapters and Appendixes in ACI 349 are updated to be consistent with ACI 318.As in previous Codes, the underlying philosophy in the design of embedments is to attempt to assure a ductile failure mode.

This is similar to the philosophy of the rest of the concrete building codes wherein, for example, flexural steel for a beam is limited to assure that the reinforcement steel yields before the concrete crushes. In the design of an embedment for direct loading, the philosophy leads to the requirement that the concrete breakout, concrete pullout, side-face blowout, and pry out strength should be greater than the tensile or shear strength of the steel portion of the embedment.