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

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Ghassem,

I guess its obvious, but don't forget to check the shears associated
with the increased moment capacity. You usually want to force plastic
moment failure before a shear failure.

cmd

-----Original Message-----
From: Harold Sprague <harold.sprague(--nospam--at)neenan.com>
To: 'seaint(--nospam--at)seaint.org' <seaint(--nospam--at)seaint.org>
Date: 08 October, 1998 4:05 PM
Subject: RE: ??Reinforcing DL's in compression??


>Ghassem,
>
>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?
>
>Re:
>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.
>
>Regards,
>Harold Sprague, P.E.
>The Neenan Company
>harold.sprague(--nospam--at)neenan.com
>
>
>-----Original Message-----
>From: Khosrownia, Ghassem NWS
>[mailto:Ghassem.Khosrownia(--nospam--at)NWS02.usace.army.mil]
>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.
>
>Ghassem.
>
>
>