Subject: RE: Steel Moment Frame - Channel to TS Colum
From: Christopher Wright <chrisw(--nospam--at)skypoint.com>
Date: Tue, 25 Jan 00 14:24:53 -0600
>Why more failures in connection? Because your connection design assumes a
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
>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)skypoint.com | this distance" (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)