We’ll arbitrarily choose a post-installed adhesive anchor. Let’s start off with a simple example that will cover the essential requirements for achieving ductility and applies to any type of structural anchor used in concrete.
Figure 1 – ½” mild steel threaded rod tensilely loaded to failure (starting stretch length = 8d) Any visible deformations could help determine if repair is necessary. During a serious earthquake, a structural system with appreciable toughness (i.e., one that possesses both strength and ductility in sufficient degree) can be expected to absorb a tremendous amount of energy as the material plastically deforms and increases the likelihood that an outright failure won’t occur.
Add strength, and a ductile steel element like the one shown in Figure 1 can now exhibit toughness. However, ductility is distinct from an equally important dimension called strength. A ductile anchor system is one that exhibits a meaningful degree of deformation before failure occurs. We’ll go over what these requirements are with a simple design example.ĭuctility is a benefit in seismic design. This blog post will focus on section D.3.3.4.3(a) for an anchor located in a high seismic region. Most building codes currently reference ACI 318 – 11 Appendix D as the required provision for designing a wide variety of anchor types that include expansion, undercut, adhesive and cast-in-place anchors in concrete base materials.
If you’re one of the many engineers still confused by the ACI 318 – 11 Appendix D design provisions, this blog will help explain what’s required to achieve a ductile performing anchorage.
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