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RE: ASD vs. LRFD

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For an anchorage that is perpendicular to the surface of the concrete (the 
usual case), the effective area is taken as a circle for convenience 
because it is easier to calculate that area than the surface area of the 
cone. The rest of the cone pull-out strength calculation is built off that 
model with the cone spread angle at 45 degrees. Hey, wait a minute...I'm 
supposed to be a steel guy! (-.

Charlie

-----Original Message-----
From:	Chris Palmateer [SMTP:chrisp(--nospam--at)vlmk.com]
Sent:	Tuesday, June 22, 1999 12:22 PM
To:	seaint(--nospam--at)seaint.org
Subject:	RE: ASD vs. LRFD

Has anyone taken a look at Section 1923 yet.  The "pull out cone" no longer
applies.  Now the calc is based on the "effective area".  This area is
defined as the projection of the cone onto the surface.  "For an anchor
which is perpendicular to the surface from which it protrudes , the
effective area is a circle."

Time to revise the "standards" I guess.

> -----Original Message-----
> From:	Paul Meyer [SMTP:PMeyer(--nospam--at)HASimons.com]
> Sent:	22 June, 1999 9:43 AM
> To:	'seaint(--nospam--at)seaint.org'
> Subject:	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.
>