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Re: Steel Moment Frame - Channel to TS Column - FR or PR Connection?

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> From: "Swingle, Mark" <Mark.Swingle(--nospam--at)>

> .....PAUL RANSOM, ARE YOU THERE?.................HELP!!......

Yawwnn! I was having such a nice nap at a paying customers expense ...

> moment connections, all of which consist of a channel section
> as the beam, and a TS as the column (1/4" thickness).  All are

> I am trying to determine whether each of the following
> connections are judged to be FR (fully restrained) or PR
> (partially restrained).
> 1.  An A36 channel, narrower than the TS, welded with CP groove

> 2.  Same as 1., except the flange welds are fillet welds both sides.
> 3.  Same as 1., except the flange welds are fillet welds one side.

I am unable to visualize the problem from this description. Is the
channel mounted with web vertical, perpendicular to a face of the TS @
centreline? If so, don't count on much stiffness. In fact, you may be
looking for problems. Probably, the weld will have little or no effect
on the connection stiffness.

#4,5 ,6 Ditto above.

> 7.  Similar to 4., except the flanges are coped and the web
> 8.  Same as 7, except with flange welds per 5.
> 9.  Same as 7, except with flange welds per 6.

Single channel on one side only? Why cope - just reverse the channel
with flanges outwards. Either way, maybe FR but you now have an
eccentricity and torsion in the column that reduces the stiffness of the
assembly and gives wierd out-of-plane deflections.

> Any comments would be appreciated, including whether CP groove
> welds are possible on A570 10 gage material.

Regardless of what is possible, ask the fabricator if they are capable.
Watch the $ signs in his eyes. Turn down the power and increase the
labour rate and fab time.

Is this a one-time issue or a manufactured product? How much will a
party in the contract lose if these cannot be assessed as FR connections
within the project schedule? Now we can talk about what is the
economical approach.

Paul Ransom, P. Eng.
Burlington, Ontario, Canada
<mailto:ad026(--nospam--at)> <>