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>From: 	JOHN HUBERT[SMTP:John.Hubert(--nospam--at)]
>Sent: 	Friday, April 18, 1997 5:33 PM
>To: 	seaoc(--nospam--at)
>Subject: 	connection between double angles
>     Does anybody know what type of weld would be used to connect 
>     back-to-back double angles to be used as a compression member?  It 
>     doesn't seem like a fillet weld would be applicable because there is 
>     no corner.  Also, section E4 (Built-Up Members) of the ASD Manual 
>     states that intermittent welds in built-up members shall be adequate 
>     to provide for the transfer of calculated stress.  Does this mean that 
>     the sum of the intermittent weld strengths must be able to resist the 
>     design axial load applied along the longitudinal axis of the member?
>     Thanks in advance for your response,
>     John Hubert, P.E.
John :

I think you have your questions on double angles as a compression member
answered .  But  here is an approach that I would do :

Considering the Double angles as a beam and simply-supported at both
Apply a concentrated load P at the mid span in  out of plane direction.
Increase the P until the combined section reach it plastic moment  Mp.
Now, you find shear  in the member due to this plastic moment.
Design the welds required by the shear ( like any horizontal shear in
Normally,  we put shim plates( or spacer plates) between the angles and
provide fillet welds.    With this approach,  the member will be good as
compression  member as well as beam member for out of plane loads.   The
basic idea is to decrease the  KL / r  and increase compression capacity
without buckling.
Hope this approach will provide you some idea.

>Kenneth  Liu,  SE

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Subject: RE: connection between double angles
Date: Tue, 22 Apr 1997 10:57:08 -0400
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Richard Lewis, P.E.
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