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GSBN:RE: pre-compression



I appreciate your clarification, Brian.  I would recommend that no
strapping or cable make a 90 degree bend around a sharp corner of a timber,
or anything else.  Corners should be eased under the strapping before
tensioning, so that the strap or cable follows a more gentle radius.  The
needed radius varies with the material, but I would think a minimum radius
might be 25mm (1").

I believe that polyester _will_ have the same concern, as will steel.
Details of the specific material and configuration matter, but every
material is subject to issues of point loading and deformation.  Perhaps
for polyester, it is less of a problem than for polyethylene, although I'd
like to see the testing to support that assertion.  In general, stretchy
things do better on this kind of cycling that harder, stiffer things, like
polyester.

Derelict

Derek Roff

--On Friday, September 1, 2006 7:23 AM +1000 Brian Hodge - Anvill
brian@... wrote:

Hi Derek,
The crease that the strapping company is referring to is not only the
crease at the buckle, but at any point along the length of the strapping
such as where it runs over timber. If the retensioning is done on both
sides it is likely that the crease will remain in the same position
across the timber, however, given that we deal only with owner builders,
I am concerned as to their capacity to reliably achieve this.
Consequently, the shift to polyester which does not have this concern.

-----Original Message-----
From: GSBN [<a  target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] On Behalf Of Derek Roff
Sent: Thursday, 24 August 2006 11:28 PM
To: GSBN
Subject: GSBN:Re: pre-compression


The manufacturers of the plastic strapping advised
me that it cannot be tensioned more than once, as the crease created
by the initial tensioning will be a point of failure.

Strapping systems vary.  On the ones that I have used, after
re-tensioning, the crease from the initial tensioning is no longer
within the tensioned section of the strap.  It is hanging loose,
unloaded, and flapping in the breeze.  Therefore, it won't be a point of
failure.  I can imagine that it might be, if I were progressively
loosening the straps, rather than tightening them.

Derelict

Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek@...

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Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek@...