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Re: helical earth anchors

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There are certain schools of thought which do not have a high regard for helical anchors.
 
Regardless, there some things can be done.
 
Predrill an augered hole, 12" -18" in dia.,  sleeve if necessary, and fill with concrete.  Use enough concrete to counteract uplift loads through DL or combined with skin friction.  Some areas of the country are simply averse to augered holes, so you need to clear this path up front.
 
Weld helical flanges onto large diameter pipe, and install the same way.  Large pipes give you some bending capacity.  These can be installed with mostly the same equipment, especially if you have a sharp contractor.
 
Use a threaded rod to attach to the hold down, and run the threaded rod down into the augered and grouted hole, deep enough to get the capacity you need.  I am not aware of any requirement for preloading testing  for holdown anchors anyway, so you can use an augered and grouted hole, in a design manner similar to concrete footings.
 
Also, an augered hole filled with concrete provides some lateral resistance and bending capacity.
 
I have not found any of these systems to work very well in liquifiable soils or in frost type situations.
----- Original Message -----
From: "Christopher Banbury"
To: seaint(--nospam--at)seaint.org
Subject: helical earth anchors
Date: Thu, 26 Apr 2007 16:38:07 -0400

Speaking of helical earth anchors and wind loads reminds me?

I am researching a method to connect helical earth anchors directly to Simpson frame hold-downs like the PHD series.

Most of the helical systems intended for anchoring temporary buildings have a coil strap or cable that is intended to wrap over or through the structure.

The top end of the helical anchor would need to have a threaded end to receive a threaded rod coupler. Most of the helical anchors I have seen rated in the 2500# range have a proprietary end.

I think there may also be an issue with pre-loading the earth anchor.

Thanks.

 

Christopher Banbury, PE

President

Ark Engineering, Inc.

PO Box 10129, Brooksville, FL 34603

22 N. Broad ST, Brooksville, FL 34601

Phone: (352) 754-2424

FAX: (352) 754-2412

www.arkengineering.net

 

 

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