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Re: Concrete anchorage (ACI 318-02 Appendix D)

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Jake,

The first thing to realize is that similar requirements have been in the ACI code for a very long time; see ACI 318 Section 15.8.3.3 which reads "Anchor bolts and mechanical connectors shall be designed to reach their design strength prior to anchorage failure or failure of surrounding concrete".  This would require that the concrete pullout strength be at least phi x fy of the anchor bolt.

Another side note is that the CCD approach is no longer a separate add to the IBC since ACI has now included it as Appendix D to ACI 318-02 therefore it will be required by any model code referencing ACI 318.

Like James I have not had to actually use this code but my personal feeling is that ACI/PCA  felt that AISC was using up all the available Greek letters and had to one up them.  With all the little factors and numerous formula I think it gives a false sense of accuracy on a system that can be highly variable depending on actual installation conditions.

I understand from others that the procedures are very conservative for larger size diameter anchor bolts which is a big hit for industrial structures.  I was also told that the developers of this procedure used some rather dubious over extrapolation of very small diameter test data.

Thomas Hunt, S.E.
ABS Consulting




"Jake Watson" <jwatson(--nospam--at)utahisp.com>

06/25/2003 07:12 AM

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Concrete anchorage (ACI 318-99 appendix D)





How many people have though about the new CCD approach and its integration into the IBC?  Reading between the lines I have drawn the conclusion that the new CCD approach & the IBC wants us to begin to think of concrete connections the same way we think of concrete beams.  Connections should be designed to fail in a ductile manner.  We are not necessarily making a better building by over-sizing anchors.  But instead, we should design the steel to yield before the concrete fails similar to a concrete beam.
 
Am I on the right track?  How many people still just use standard "over-sized" connections that are strong enough, but don't fail in a ductile manner?  Or is this another code provision that will be repealed in a few code cycles?  Any thoughts?
 
Jake Watson, P.E.
Salt Lake City, UT