Guide for Design of Anchorage to Concrete: Examples Using ACI 318 Appendix D

Description

This guide was prepared by the members of ACI 355,Anchorage to Concrete, to provide design examples thatdemonstrate the provisions of ACI 318-05 Appendix D.Appendix D, which was first introduced in ACI 318-02,contains design provisions for determining the strength ofanchors based on the Concrete Capacity Design (CCD)method for concrete breakout failure. The CCD method hasits origins in research work done at the University of Stuttgartin Germany (Eligehausen et al. 1987; Eligehausen and Fuchs1988; Rehm et al. 1992) and was formalized at the Univer-sity of Texas at Austin in the 1990s (Fuchs et al. 1995). The CCD method calculates the concrete breakout strength usinga model that is based on a breakout prism having an angle of approximately 35 degrees, rather than the traditional 45-degree cone model used since the early 1970s.Appendix D design provisions are for both cast-in-place anchors and prequalified post-installed mechanical anchors.

Separate design equations are frequently provided becausecast-in-place anchors behave differently than post-installed anchors. The provisions for post-installed anchors are onlyintended for those post-installed anchors that are qualifiedunder comprehensive testing protocols. The testing and evalua-tion requirements in ACI 355.2 are the standard for qualifyingpost-installed anchors used in design with Appendix D.Similar procedures, which are expected to be completedsoon, are under development for adhesive anchors andconcrete screw anchors.

The example problems presented in this guide were developedusing the code provisions in Appendix D of ACI 318-05,which were current at the time the examples were developed.The new provisions of ACI 318-08 will alter the calculationsand results in these examples. Commentary in this guidedescribes how the new ACI 318-08 provisions modify thedesign results. The ACI 318-08 Appendix D provisionsclarify issues when dealing with earthquake forces, ductilefailure, anchor reinforcement, and supplemental reinforcement.