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RE: ??Reinforcing DL's in compression??

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The master for this type of problem is Ray Tide at Wiss, Janney & Elstner.
He has written several articles on reinforcing steel elements under load.  I
have reinforced steel members also by welding reinforcing elements under
load.  You need to evaluate your existing load, the final load on the
element, and the effect of welding.  

I generally like to develop a welding procedure to minimize heat input.  The
element will deform due to the welding process.  I don't think that I know
enough about your problem to advise you on a final solution.  

Additional questions are:
Is it a case of adding section to increase area to drop the stresses?
Are you adding section to increase the radius of gyration
Is the end connection adequate?

1.	AISC Engineering Journal, 4th quarter, Reinforcing Steel Members and
the Effects of Welding, by R. H. R. Tide.  
2.	Proceedings, AISC National Engineering Conference, New Orleans,
April 1987, Basic Considerations When Reinforcing Existing Steel Structures,
R. H. R. Tide.

Harold Sprague, P.E.
The Neenan Company

-----Original Message-----
From: Khosrownia, Ghassem NWS
Sent: Thursday, October 08, 1998 9:05 AM
To: 'SEAOC List Server'
Subject: ??Reinforcing DL's in compression??

I have a consultant who proposes to reinforce an underdesigned DL truss
diagonal by welding additional plate to their projecting legs. The area of
steel required is based on the required additional capacity needed. For
welding design, the consultant is using the full axial load in the combined
section in order to determine the length of weld. While this may produce
conservative results, I feel like the approach is not logical. I think the
plate should be attached to the hosting DL's in such a manner to be stable
in compression and to be able to contribute the lacking strength. If the
plate should provide 10 kips of additional capacity, then its weld spacing
should be determined based on stability of the plate in compression, and
allowable compressive stresses associated to that.

What do you think?

I appreciate all comments.