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RE: ROCK ANCHOR PROOF TESTING

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Shawn-
You need to have a clear understanding of what it is you are trying to 
test.  Usually you want to have assurance that the anchorage will develop 
more than the design load of the anchor so you have a reliable estimate of 
the capacity that you can rely on.  There are two types of loads commonly 
used: pull out tests (where you purposely fail the anchorage to determine 
the ultimate in situ bond stress between the rock and the grout. This is 
usually done on a small number of anchors to assist in determining anchor 
size and ultimate loads for design) and performance tests (where the anchor 
is pulled to a specific load, partially unloaded then loaded to a higher 
level with the cycle repeated up to a prescribed level , e.g., to 1.33P, 
where P= Design load for the anchor.  Movements are recorded during each 
cycle to establish the residual set in the anchor.  A simple test, the 
proof test, used in conjunction with the performance test, can be used to 
quickly pre-load and test each anchor during installation. )

A fairly complete description of the process including a commentary can be 
found in Chapter 4 of the "Post-Tensioning Manual (PTI)", 5th edition 
(1990), Post-Tensioning Institute, Phoenix, AZ.  We use these procedures 
quite successfully in seismically upgrading large water storage tanks.  The 
descriptions and commentary in the PTI Manual are well written and easy to 
follow.

Bill Cain, S.E.
Oakland, CA


-----Original Message-----
From:	Freilinger, Shawn W [SMTP:Shawn(--nospam--at)Valmont.com]
Sent:	Monday, October 12, 1998 15:18 PM
To:	'SEAINT Mailing List'
Subject:	ROCK ANCHOR PROOF TESTING

		I am design a rock anchor foundation for a
telecommunications tower.  Is anyone familiar with proof testing of these
rods?  The anchors are about 11' deep into solid bedrock.

		My company has required a couple different ways of proof
testing these in the past.  One method is to grout the bottom 1/3 of the
hole and then pull with a third of the expected anchor tension.  The other
method is to grout the entire bar and then proof test it for combined
stresses (bending and tension).

		If anyone has some "standard practice" knowledge or reading
resources, I would appreciate it.

		Thanks,
		Shawn

		Shawn Wicks Freilinger
		Valmont/Microflect
		Shawn(--nospam--at)valmont.com <mailto:Shawn(--nospam--at)valmont.com>
		(503) 315-4515