To: "INTERNET:seaint(--nospam--at)seaint.org" <seaint(--nospam--at)seaint.org>
Subject: Fw: ACI 355.2 - Proposed Test Criteria for Post-Installed Anchors
From: Peter Higgins <76573.2107(--nospam--at)compuserve.com>
Date: Wed, 14 Mar 2001 20:46:32 -0500
As one who specifies literally tens of thousands of these each year, I must
agree that ACI is fixing something that isn't broken.
Expansion anchors have performed extremely well for decades, and in
numerous earthquakes (where they ripped apart a slab in one failure after
the shelving structure failed and put them into extreme tension).
If expansion anchors had a fundamental problem, we would have known long
before now as these anchors would have pulled up all over the place in past
earthquakes. It simply hasn't happened.
The point of the revised testing is theoretically sound, and the test
protocol of artificially creating a crack and installing the anchor into it
is intuitively attractive. However, the protocol then completely ignores
the mass restraint present in the typical slab by taking off all
confinement forces before testing for tension. This is neither
theoretically or practically correct as has been proven many times in the
Clearly, any anchor requiring any side reactions from the hole will fail
this test, leaving only undercut anchors available to resist tension. If
this is the case, we'd better remove all our expansion and expoxy anchors
from existing slabs. Per ACI 355, this should be a cinch. Try prying even
one of these well set anchors from any slab of any age, see how easy it is
and then decide if Murphy isn't correct once again: Don't fix it if it
This is simple, practical engineering, and completely ignores the lawsuit
issue which may or may not have merit. However, one must question the
outlawing of well established materials with known performance records.
When that happens, it is usually the theory that is wrong, no matter how
attractive and intuitive it may seem.
Peter Higgins, SE