Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: How Can Force in "All Thread" be Det

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Rather than using a strain gauge attached to the all thread you could
use an Extensometer to measure the elongation.  I used this when I was
testing some all thread while I was in college and it worked well.  The
link below is to a company that sells testing equipment.

 http://www.testresources.com/strainwiz.htm

Lars Holte



-----Original Message-----
From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com] 
Sent: Wednesday, October 10, 2001 4:05 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: How Can Force in "All Thread" be Det


Bill,

I understand the method that you describe, but wonder how that would be 
applied to GLBs with cantilevers.  I can see how this could be applied
in 
reducing the positive moments by lifting the center portion of the beam,
but, 
in reducing negative moment, wouldn't the change in moment be reflected 
in movement at both the end of the cantilever *and* at the center of the
span?

I have 4 different beam configurations that need to have moments
reduced, 
some just in the positive moment area; another in both the positive
moment 
area *and* at both cantilever supports; another at one cantilever
support and 
I don't want to give the sub-contractor a lot of confusing information.

I have used prestressed strand before anchored to brackets with strand
chucks 
(not proprietary wedges) and that has worked well, but this
sub-contractor 
"can't find anyone who knows" what I want and he wants to use all thread
but 
doesn't know how to determine the tension force in it.  (Other than
using 
load cells, neither did I.  I did mention strain gauges for smooth rods,
but 
that wouldn't work with a threaded bar.)

Roger Turk
Tucson, Arizona

You wrote:

. > Roger-
. > What Michael suggests brought back memories of a "prestressing"
. > reinforcement I did of a series of trusses about 25 years ago. The
bottom
. > chords had failed on several adjacent trusses.  We shored the panel
points
. > and replaced the bottom chords. Then we added prestressing bars on
each 
. > side of the truss. To monitor when the dead load was carried by the 
. > trusses, we place a shore with a load cell under the center panel
point.  
. > When the load went to zero, we knew the dead load was being carried.
You 
. > could probably do something similar with the "all-thread."

. > As a side note, I was in the very early part of my career (about 5
years 
. > out of school).  The carpenter foreman was quite skeptical that by
jacking
. > horizontally one could make the truss lift.  He protested vigorously
but 
. > did what I asked. He kept muttering about "college boys."  When we 
. > stressed the first truss, the load on the load cell hardly moved as
we 
. > stressed the bars. He kept saying, "This will never work. See, the
bar 
. > load is getting higher and higher and the vertical load hasn't
changed at 
. > all (not quite true but the change was a very small reduction." We 
. > reached nearly the design load on the bars (we had load cells on
them 
. > too) when all of a sudden, the load on the load cell under the
center 
. > panel point went rapidly to zero and the shore toppled. The foreman
stood 
. > there silently for several minutes with his mouth wide open. Finally
he 
. > said, "well, I'll be damned. The college boy does know what he's
doing." 
. > From that point on, I had his complete cooperation!

. > Regards, 
. > Bill Cain, SE
. > Oakland CA

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ******** 


******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ********