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RE: ASD vs. LRFD

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Title: RE: ASD vs. LRFD

Similarly, anchors into concrete used to be designed based on the "bond strength" between the steel and the concrete, resulting in some very deep embedments of anchors.  Now we design based upon a "pull out cone" and the required embedments of anchors is much less.    For example, our corporate "standard" for 25 mm (one inch) anchors has gone from 600 mm (24 inches) embedment  for a hooked anchor to 250 mm (10 inches) for an anchor with a nut and washer on the bottom.

This doesn't mean that the old method was "wrong" in that it caused failures, but it was "wrong" in that it resulted in wasting material and was based upon an incorrect understanding of what kept the anchor in the concrete. 

> Isn't it somewhat irresponsible to call a design method
> "wrong" when the
> method was accepted and used for over 4 decades by all
> structural engineers
> on the continent of North America and was never questioned as to its
> correctness and engineering validity ???

See my comment about the method used to design two-way slabs 80 years ago.

Was it "accepted"? Yes.

Did it "work"? Yes.

Was it "wrong"? Yes.