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RE: HILTI Anchors for Vessels

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I don’t know if this helps any, but Hilti does make a tension zone tested adhesive anchor called the HVZ.  It is not common here in the US but I understand it is used overseas where the requirements for cracked concrete testing have been around longer (this is based on my vague recollection of a conversation with another manufacture’s rep earlier this week…)

 

http://www.hilti.com/holcom/modules/prcat/prca_navigation.jsp?OID=-9791   

 

 

Michelle Motchos, PE

STEVENS & WILKINSON OF SOUTH CAROLINA, INC.

Columbia, SC 

 

 

 

-----Original Message-----
From: Padmanabhan Rajendran [mailto:rakamaka(--nospam--at)yahoo.com]
Sent: Thursday, March 16, 2006 9:04 AM
To: seaint(--nospam--at)seaint.org
Subject: HILTI Anchors for 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 the surface will crack?

Please share your thoughts and experiences, if any.

Thanks.

Rajendran


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