Need a book? Engineering books recommendations...

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

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

[Subject Prev][Subject Next][Thread Prev][Thread Next]
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

-----Original Message-----
From: Michael Bryson [mailto:MBryson(--nospam--at)mhpse.com]
Sent: Tuesday, October 09, 2001 5:20 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: How Can Force in "All Thread" be Determi


Can't you determine the force by the amount the GLB will deflect upwards?

-----Original Message-----
From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com]
Sent: Tuesday, October 09, 2001 3:42 PM
To: SEAOC Listservice
Subject: How Can Force in "All Thread" be Determi


I have a project reinforcing glue-laminated beams in an existing wood 
panelized roof of an industrial building and have specified using 
prestressing strands to do the reinforcing.  The contractor wants to use 
"all thread," however, I cannot think of a way to measure the force in the 
"all thread" as it is being tightened.  The situation is such that the force

in the "all thread" *has* to be measurable as the roof has a combination of 
simple span, single cantilever and double cantilever GLBs.

TIA

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

******* ****** ******* ******** ******* ******* ******* ***
*   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 
******* ****** ****** ****** ******* ****** ****** ******** 

******* ****** ******* ******** ******* ******* ******* ***
*   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 
******* ****** ****** ****** ******* ****** ****** ********