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RE: Steel Moment Frame - Channel to TS Colum

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>Why more failures in connection? Because your connection design assumes a
>perfect rigidity.
Not at all. The tendency seems to be to design connections that can't 
handle discontinuity loading produced by the attachment. Guy assumes pin 
ended beams (worst case--for the beam, anyway), and figures the welded 
connection at the end to handle only the vertical reactions. Turns out 
that a moment develops at the ends (because the ends are attached to the 
rest of the structure) that the weld can't handle and the connection 

As I've mentioned, I don't do buildings, so I don't get into a lot of 
angle brackets or beam seats, which may easily have a finite stiffness. 
Typically a crane structure or a machinery support simply connects member 
to member, either welded or bolted. The weld or the bolt pattern is 
characteristically much stiffer than the rest of it, and needs to support 
cyclic loading. 

>By the selected connector dimension, we can claculate the connection
>stiffness, and then compare the "calaulated connector stiffness" and
>"REQUIRED connector stiffness".
I think I'll stick to my guns--providing a specified stiffness in my part 
of the the world is rather tricky and goes a lot further than calculating 
deformations out of Roark, even in the case of simple springs. There's a 
paper on one of the NASA sites (If you're interested I can supply a URL) 
illustrating the stiffness of a bolted connection. Looks like quite a 
job, even with all the idealizations that affect the accuracy. Hard to 
imagine doing this without a flight hardware QA system to go along.

Mind--I'm not denying that connector stiffness exists. I _am_ saying that 
as a practical matter, it seems advisable to overkill the connection a 
bit to be sure it stays elastic under the worst possible load.

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