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Re: Structural steel--isolated joints

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>How so?
Flexible supports reduce the response frequencies and increase the 
amplitudes and decrease the damping. The higher the response amplitudes 
the higher the stress. 

>We need the lateral support to resist the crane thrust perpendicular to the
>crane rail. Do we need it for the vibrations?
Yes, although what you really need for the vibrations is to fix the crane 
rail alignment. 

>That is why there is the big gap in the bolted connection of
>the lower plate.
I forgot to mention the bolts. The way they're mounted in there with a 
free length of shank between the plates guarantees fatigue failure. 

When I see a crack like you show in the picture, weld repairs and 
construction details like those bolt installations, my first reaction is, 
'Run away! run away!' There are reasons why that section of pipe cracked 
and why the crane rail installation seemed to need more lateral support. 
Before I did anything else I'd want to make sure I understood those 
reasons before I assumed that the present installation is even safe, let 
alone satisfactory. The connection may be just today's weak link. If you 
strengthen that, you may just be moving tomorrow's failure to someplace 
even less desirable.

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw(--nospam--at)        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)

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