ACI 318-08 Appendix D
ACI 318-08 Appendix D
(OP)
I'm curious if anyone has read the new ACI318-08 Appendix D, Section D3.3.6? Am I understanding correctly that if the anchor material is brittle, then the anchor design strength is limited to 0.4 x concrete failure strength per D3.3.3?
Why is the brittle anchor design strength a function of the concrete failure strength? If I have a very weak brittle anchor (say and old existing anchor) and very strong concrete, how is this properly calculating the steel failure mode in the anchor?
Thanks,
Stan
Why is the brittle anchor design strength a function of the concrete failure strength? If I have a very weak brittle anchor (say and old existing anchor) and very strong concrete, how is this properly calculating the steel failure mode in the anchor?
Thanks,
Stan






RE: ACI 318-08 Appendix D
I think the idea is that an anchor that can deform plastically prior to failure can reduce the loading transferred to the concrete, whcn compared to one with the same ultimate strength that doesn't yield. Partly through reduced motion transferred, partly though increased damping when things start stretching plastically.
RE: ACI 318-08 Appendix D
RE: ACI 318-08 Appendix D
That being said, 318-05 has a similar provision, but it only applies to seismic loads in SDC C, D, or E. It doesn't say anything about using the concrete capacity instead of the steel capacity, it just says the "minimum design strength of the anchors shall be at least 2.5 times the factored forces transmitted by the attachment". This reference is in IBC 06 on page 379 - this modifies a portion of App. D in ACI 318-05.
The anchor capacity is the lowest of the different concrete failure modes and the steel.