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Re: HILTI Anchor for anchoring Vessels; now Covert.

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Go to the ICC website and download Covert's ER-4846 Legacy Report, which should provide you with the allowable shear and tension capacities for various configurations.  It is a 17 page .pdf file.   On some powerhouse projects, Covert is the required anchor.

Neil Moore, SE, SECB
neil moore and associates
shingle springs, california

At 12:41 PM 3/17/2006, Padmanabhan Rajendran wrote:


1. I did not see any tables and charts to design Covert, Undercut anchor at their web site. Does it mean that I prescribe the loads and the Company designs on a case by case basis?

2. Hilti recommends tensioning epoxy anchors. So, what may be your objections to it?


Harold Sprague <spraguehope(--nospam--at)> wrote:
I have used a Covert "Ductile Undercut Anchor" post installed mechanical
anchor rod and tensioned the anchor rods after installation.
On the applications that I have employed, the bolts were checked after a
week and showed no relaxation.

I would advise against tensioning an epoxy anchor.

Harold Sprague

> ----- Original Message -----
> From: Padmanabhan Rajendran
t; To: seaint(--nospam--at)
> Sent: Friday, March 17, 2006 6:58 AM
> Subject: HILTI Anchor for anchoring Vessels
> A client wants to set a vessel (8' dia X about 55' tall) on an existing,
>2' thick, concrete mat, and anchor the vessel to the mat with 1" dia HILTI
>epoxy grouted anchor rods. The tension and shear in the bolt is 11000 lbs
>and 1000 lbs respectively. My scope of work is to determine the bolt
>embedment depth. I understand that the bolt will be pretensioned after the
>vessel is installed.
> I used the published values of nominal bolt loads, adjustment factors
>for edge distance and bolt spacing etc. to calculate the bolt embedment
>depth. One of the standard embedment lengths (12.375") is sufficient to
>support the vessel.
> What bothers me is that the post-installed epoxy anchors are not
>approved by ACI 318 (See Appendix D for Scope of application) mainly
>because the reliability of these type of anchors has not been certified in
>accordance with ACI 355.2. However, the published bolt values in HILTI
>catalog have been certified, by ICC Evaluation Service, to conform to UBC
>1997, and 2000 IBC. The certification stipulates that it is valid only when
>the concrete is uncracked. The restriction stems from the fact that the
>anchors were not tested in cracked concrete environment.
> The current thinking in anchor bolt design is that the headed bolt, or
>something similar, is the most effective anchor element. It is reported
>that L- shaped and J-shaped bolt perform poorly, in comparison. If L-shaped
>and J-shaped bolts perform poorly, how can a straight piece (despite having
>threads) perform any better?
> Is it possible to pretension an, un-sleeved, anchor bolt? Is it not
>likely that concrete near t he surface will crack?
> Please share your thoughts and experiences, if any.
> Thanks.
> Rajendran
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