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Re: distortion from heating

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I am not sure about the answer to your question.
However, I was involved in the insurance claim against a contractor with a
backhoe or shovel on a flatbed that ran into the bottom flange of a plate
girder. There was a 15 degree (or so) twist to the beam with failure of the
cross-bridging. New York State Transportation Highway Department employees
did the work to restraighten the girders. Bridge over I87 near Syracuse I
think. The idea was heat the steel to just enough to avoid cracking while
bending. It was a very long process. They might be able to provide some
insight. I am sure you can get their number off of the internet. I spoke
with people at the Ministry of Transportation in Ontario and they said they
very very rarely use this method as it is too expensive. Extra blocking or
cross bridging near the location to stop twisting is used.

David Handy
The Thompson Rosemount Group
Cornwall, Ontario, Canada
----------
> From: RoyLevy(--nospam--at)aol.com
> To: seaint(--nospam--at)seaint.org
> Subject: disortion from heating
> Date: Tuesday, January 05, 1999 4:36 PM
> 
> Many years ago I heard of a team of technicians who had developed a
technique
> to straighten deformed steel bridge structures  in place by flame-
> straightening.
>  
> To help me understand the principles, this is my question:
> 
> Assume a steel plate say 3/8" thick by 4" wide and 3 ft long, simply
supported
> at the ends, say resting on a pair of saw horses.   Heat is applied
across the
> top at the center, for example by welding a 1/4 x 4 " wide gusset plate
at the
> center, across  and perpendicular  to the plate ( 2  3/16"  f illet
welds, 4
> '' long , for example)  .
> 
> Will the center of the plate rise or will it sag ?  In another form, the
> question is which will prevail -  The loss of rigidity while the top is
molten
> or the contraction effect upon cooling?
> 
>