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Re: ACI procedures for 355.2 test method

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I located the following in the archives from August 20 of last year.  At
least one of the list server participants was trying to raise interest in
the topic.

--------

<< Currently there are code changes in development that will dramatically
effect the future analysis, design, and use of post-installed mechanical
(expansion) anchors in "Cracked Concrete".  Some of the anchor types
effected by these changes are known by the generic names wedge, sleeve,
and drop-in.

Initially, these new standards are to be introduced as provisional
standards of ACI 318.XX.  Eventually, they will be incorporated into the
IBC XXXX.

The code changes were developed with the basic assumption that after
expansion anchors are installed (within a tension zone), cracks that
develop tend to pass through the anchor locations.   It is assumed that
anchor installation stresses also contribute to tension zone cracking
and that as much as 90% of all installed anchors will "attract" a crack.

It is anticipated, these code changes will require substantial
reductions in the tension and shear capacities of the most commonly
specified post-installed anchor types.  As a result, current anchor
systems will have inadequate capacities to meet designers/specifiers
needs.  New anchor systems will need to be designed to meet these new
requirements.

I have not seen any of these conditions myself, nor have I heard of this
ever happening in practice.  I would like to know if the potential
results assumed by these standards are supported by real-life anchor
performance.

Please, would all interested parties respond to the questions listed
below.  If you have any additional comments, questions, or opinions that
would promote further discussion on this subject it would be greatly
appreciated.

1.  Are you aware of a situation/installation where a tension zone
crack, through a post-installed anchor location, has contributed to, or
resulted in an anchor failure?

2.  Are you aware of a situation/installation where a tension zone
crack, through a post-installed anchor location, has reduced an anchor's
capacity (tension or shear)?

3.  Do you have any historical, real world data that would indicate
post-installed fastenings contribute to, or are effected by tension zone
cracking?

Thank you,

Kent Carlson, P.E.
STI Consultants >>

---------

Regards,

Rick Drake, SE
Fluor Daniel, Aliso Viejo, CA

**************************





Peter Higgins <76573.2107(--nospam--at)compuserve.com>@compuserve.com> on 03/19/2001
05:54:22 PM

Please respond to seaint(--nospam--at)seaint.org

To:   "INTERNET:seaint(--nospam--at)seaint.org" <seaint(--nospam--at)seaint.org>
cc:

Subject:  ACI procedures for 355.2 test method


I have just contacted ICBO and received some very disturbing news.

ACI has already presented the test method for incorporation into the ICBO
ES methods. The presentation was made in January, 2001, and the public
comment period closes today (!)

While the draft ACI 355.2 is indeed a test method, not a code, this is most
certainly not true of the ICBO standards. They are adopted by reference
into the building codes, and most jurisdications use them faithfully.
Therefore, if ACI 355.2 methods are adopted by ICBO, then they become a de
facto code.

I have two questions for ACI:
1) Why is a "draft" standard being presented to a code publishing body in
advance of the formal adoption and public comment period?
2) Why are hearings being conducted at the convention in advance of the
close of public comment, while no further meeting is scheduled? Do they not
plan to meet later to consider the public comments?

I have also contacted some of my colleagues in the EU where this test
method was first proposed and then adopted. It seems that a similar
"stealth" change in the EU standards was used to get the same test method
adopted. Indeed, I have been told that the EU approval was influential in
the decision of ACI to adopt the method. I can report the following:
1) The EU has rescinded the approval of the test method for all but
extraordinary life safety structures (where these things don't get much use
anyway).
2) There are a lot of unhappy engineers over there who feel they've been
had by a company trying to corner the market on concrete anchors.

Again, I must consider the question: Why are we in such an all fired hurry
to stop the use of mechanical and epoxy anchors in concrete? I haven't seen
any anecdotal reports of failures in any earthquake, let alone the sort of
evidence normally required to outlaw something this fundamental.

Something like this should be given a great deal of consideration. There
are literally millions of these anchors used every year. In 1997 ICBO ES
required the manufacturers to provide additional testing to allow further
use of expansion anchors for wind and seismic loads. After testing, these
anchors were certified with the 33% load increase (i.e. for more load than
the previous approvals). Is ICBO wrong again? I doubt it.

Whenever I see a rush to judgement, and things trying to be codified before
they have even received their mandatory comment period, there are only two
explanations:
a) There's a genuine emergency and something needs to be fixed immediately
(e.g. the Northridge Steel Connection detail)
b) Someone doesn't want enough time to pass for the cold light of day to
shine on the issue and see it clearly.

I don't see an emergency anywhere, so I beginning to be left with the
second alternative.

If anyone has more info, I sure would like to hear it.

Peter Higgins, SE









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