Need a book? Engineering books recommendations...

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

Re: Bolt retightening

[Subject Prev][Subject Next][Thread Prev][Thread Next]
> From: Kevin Below <kevinbelow(--nospam--at)videotron.ca>

> I am in need of some guidance on the right technique for retightening
> bolts on a 40-year-old steel structure.
> One of my clients, suspecting that the bolts in one of their many
> buildings were loose, asked me to check.  Surprisingly, we found that
> his suspicions were founded.  

That's really bizarre ... A client who knows enough to realize that he
has loose nuts!

> My first question is whether I should require new bolts, since I have no
> control or knowledge of the existing bolts.  It seems like a good idea,
> especially if I need to calibrate the torque wrench.

Not certain about the bolt options from 1966. I sustpect that you could
have A325. Check for marks on the head and nut.

> Also, the idea of a machine to calibrate the torque wrench each day
> seems overkill to me, when this building doesn't seem to have suffered
> in its loose state for so long, surviving mild earthquakes and strong
> winds with no sign of distress, despite its lack of tightened bracing.
> Would the turn of the nut be sufficient, or is this really only for
> bearing type connections ?

Turn-of-Nut is the ONLY method that the CSA S16 recognizes for
tightening for slip-critical connections. It is NOT required for bearing
connections since they do not need to have the full tension in the bolt.
Anything else is a method of confirming tightness (i.e. inspection). DTI
washers are now explicilty acceptable for inspection, as well.

Even if you calibrate your wrench, you still have to achieve the
Turn-of-Nut requirements and match mark the nut/bolt prior to impacting.

A325 bolts are considered to be reusable if you can run the nut for the
full length of the thread with your fingers. There should not be visible
damage to the shank.

-- 
R. Paul Ransom, P. Eng.
Civil/Structural/Project/International
Burlington, Ontario, Canada
<mailto:ado26(--nospam--at)hwcn.org> <http://www.hwcn.org/~ad026/civil.html>

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