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ACI 318 Appendix D detailing

ACI 318 Appendix D detailing

ACI 318 Appendix D detailing

(OP)
Hi, I've working on anchorage design and have a quick question. ACI 318-11 section D.3.3.4.3 and ACI 318-14 section 17.2.3.4.3 both give requirements for the design tensile load on anchors with high seismic forces. One of the requirements (sub-section a) basically allows us to design the anchor so that the steel strength controls over the concrete strength (ensures a ductile failure). In order to use this, there is a requirement that the anchor have a stretch length of at least 8 times the diameter. I've seen a couple ways of detailing this requirement from using a bond-breaking tape around the anchor to using an anchor sleeve. My question is in regards to the anchor sleeve. How do you normally detail out the sleeve and anchor bolt? Do you leave the void between the sleeve and the anchor empty or fill it with a grout or epoxy material? If you leave the void empty or use an epoxy, how are shear forces transferred to the foundation without imparting a bending moment on the anchor? If you fill it with a grout or epoxy will the anchor still be allowed to stretch or is there something else you do to maintain the ability to stretch (non-threaded anchor maybe)? Thanks for the help!

RE: ACI 318 Appendix D detailing

Keep in mind that to restrain the anchor from stretching will require a high bond strength; I would imagine that unless you have quite the expansive epoxy or grout that you're unlikely to get significant residual bond through the bond-breaker. I'd fill it full of epoxy or grout for the lateral support of the anchor bolt as you mentioned.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

RE: ACI 318 Appendix D detailing

(OP)
Yeah it seems like the best thing to do is to fill it with a cement or epoxy grout and then either use a rod with an unthreaded portion within the sleeve or to use a fully threaded rod with the bond breaking tape to ensure the ability to stretch.

RE: ACI 318 Appendix D detailing

Can you use an extended anchor rod that is pre-tensioned (giving it some length to 'stretch')

Dik

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