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Re: Bolt retightening

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That phone number is still good and it's Mike Gilmor.
Gary

On 27 Sep 2005 at 11:39, Daryl Richardson wrote:

> MessageKevin,
> 
>         The man you want to talk to is Mike Gilmore at CISC.  They
>         have a web site at cisc.ca.  The telephone number I have is
>         (416) 491-4552 but that might be out of date.
> 
> Regards,
> 
> H. Daryl Richardson
>   ----- Original Message ----- 
>   From: Kevin Below 
>   To: seaint(--nospam--at)seaint.org 
>   Sent: Monday, September 26, 2005 8:48 PM
>   Subject: Bolt retightening
> 
> 
>   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.  The roof structure of this warehouse type
>   building is the Gerber type (cantilevered beams alternating with
>   suspended spans), and the beams that pass over the columns have 4
>   bolts in the connection. These bolts are almost all loose.  You can
>   unscrew them by hand. The original drawings call out hi-tensile
>   bolts in non-slip connections, which is obviously not what they got.
>   There is no bracing in the building, and no concentric masonry
>   walls, so I presume the lateral resistance comes from the non-slip
>   joints of the beams over the columns, forming rigid connections.  In
>   this case, the beam-column connections should rightly be non-slip,
>   and not bearing type. So now I have to prepare plans and specs for
>   tenders for the job of tightening the bolts. My search of the steel
>   manuals and text books and web sites leads me to conclude that it is
>   not simply a case of applying a torque wrench to these bolts.  In
>   the old Canadian steel code (oh yeah, this job is in Canada), the
>   required torque was specified, but now it appears that a
>   predetremined torque does not always produce the required bolt
>   pretension.  So each shift, the guy using the torque wrench should
>   calibrate his torque wrench with the type of bolt to be installed,
>   on a machine that measures the pretension.
> 
>   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.
> 
>   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 ?
> 
>   What do the steel gurus think ?  
> 
> 
> 
> 
> 
>   Kevin Below, ing., Ph.D.
> 
> 
> 
> 
> 
> 
>   --
>   No virus found in this outgoing message.
>   Checked by AVG Anti-Virus.
>   Version: 7.0.344 / Virus Database: 267.11.7/112 - Release Date:
>   2005-09-26
> 
> 



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