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Re: Epoxy Anchors - Boston Tunnel
- To: seaint(--nospam--at)seaint.org
- Subject: Re: Epoxy Anchors - Boston Tunnel
- From: coengineer(--nospam--at)aol.com
- Date: Mon, 17 Jul 2006 13:46:36 -0400
The City of LA does not typically allow anchor products to have a higher capacity than the values listed in the 1997 UBC Table 19 for the same diameter. So a 1 inch diameter anchor with special inspection in 2000 psi concrete is based on the 7 inch embedment which has an allowable tensile load of 5700 lbs. If a manufacturer tests with a deeper embedment and the anchor has an average ultimate of 50000 lb, LA will still restrict the capacity to 5700 lb.
Do you recall the cause of the anchors spinning in the hole on your project?
Also, regarding the viscosity of the adhesive being too thin, it appears in the photos that a hole plug was used to prevent this (red plastic plug).
Howard Silverman, PE
Covert Operations/USP Structural Connectors
Sent: Mon, 17 Jul 2006 10:29 AM
Subject: Epoxy Anchors - Boston Tunnel
The use of epoxy anchors for overhead applications is an interesting one. I did a design on retrofit pipe hangers on a bridge here in Washington State a couple of years ago and was going to use undercut anchors for an overhead installation, but was told by the highway department to change them to epoxy anchors. I never could figure out why they would think epoxy is superior.
I also was looking up the ICBO/ICC test report for some Hilti anchors recently, and in one case anyway (ER-5193) noted that the City of Los Angeles and downgraded the allowable load values considerably for these epoxy anchors, particularly for the larger diameters and deeper embedments. I don’t know what that was based on, but it would be interesting to find out.
I have a lot of faith in post-installed anchors if they are properly installed and inspected, but have my own horror stories which have included going on the “completed” job and being able to spin an anchor in the hole with my fingers. These things really need rigorous special inspection when they are in critical locations.
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