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Re: big dig structural failure - epoxy anchors overhead supporting gravity

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Chris-

We did lots of cyclic tests (only a few 100 cycles though)  but no repeated sudden  (impact?) loads.

The cyclic chemical anchor tests I did were nearly 10 years ago.  I cannot remember what ICBO AC I used, but the tests involved a few hundred cycles at various load levels (about 3 or 4 levels, I think).  The cyclic load rate was something in the 1/2 Hz  to 1 Hz range.

Pass pass / fail was for the anchor to make it through the all the test cycles, being able to achieve the desired load levels.  The test protocol was load controlled so that if an anchor "got soft" the test apparatus continued to apply displacement until the load was achieved or the anchor pulled out.

As the test program proceeded we could easily tell at the very begining of a test if anchor was going to pass / fail. 
If the low load level displacements were anything but miniscule we could tell "this anchor ain't gonna make it".

ICBO ES "allowable design anchor load" was based on the amplitude of  the load sequence that the anchor could survive

It seemed  to me whether an anchor was going to survive a given load level was  related to the strain levles in the bonding material.

On 7/16/06, Christopher Wright < chrisw(--nospam--at)skypoint.com> wrote:

On Jul 16, 2006, at 12:47 AM, Robert Kazanjy wrote:

> I think SImpson reudces their values depending on hole cleaning
> method, they even have a value for "no cleaning" but I'm sure there is
> a huge scatter on those values & I'd be reluctant to use those values.
Just out of my own curiosity, does anyone ever subject these items to
cyclic loading or repeated sudden loads? I'd expect that repeated loads
would reduce the capacity over time.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
http://www.skypoint.com/~chrisw/


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