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RE: Post yielded beam performance

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Local flange replacement requires a lot of cutting and welding.  The beam
apparently is a hot rolled section that can be heat straightened without any
detrimental effects.  My first option would be to straighten the beam with a
torch.

If the numbers indicate that the beam needs to be supplemented with a Tee,
plates or bars refer to the articles by Ray Tide of Wiss, Janney & Elstner.
(Referenced in a previous post)

Harold Sprague, P.E.
The Neenan Company
harold.sprague(--nospam--at)neenan.com


-----Original Message-----
From: yenem(--nospam--at)iinet.net.au [mailto:yenem(--nospam--at)iinet.net.au]
Sent: Sunday, November 15, 1998 10:09 PM
To: seaint(--nospam--at)seaint.org
Subject: Post yielded beam performance


I hope that some of you experienced with post yielded beam behaviour can
help me with the following problem.

An I-beam supporting mechanical equipment above a large ore bin has at some
stage been overloaded and has

a) local flange buckling
b) a large deflection (approximately 30-40mm over a 4.5m span) which may be
found to be inelastic when the load is removed

The flange buckling doesn't occur in the middle of the beam, which is
laterally braced with a truss arrangement.  I think that the buckling was
caused by a construction load applied to the top flange eccentrically
causing the member to twist between points of lateral restraint.  This does
not necessarily support the excessive deflection case but there is evidence
of twist on adjacent beams which would only ever normally carry relatively
light floor grating loads.  Perhaps a load was hung from the two adjacent
beams using a cross member which rested only on the flages and not over the
web.

What are the issues regarding the strength of this beam given it has
excessive deflection / deformation, and that a section of the beam has
twisted flanges?

The deflection is not an issue from an aesthetics point of view - you cannot
see the beam and its on a mine site anyway! - but if it is the result of
yield sections what then?

Is it necessary to remove and replace the beam, or could

a) local flange replacements be made;

b) a tee section be welded to the underside if it is found that the beam is
deficient for the design loads;

a) and b)

Any responses would be greatly appreciated.

Regards

Dave Meney
Structural Engineer
Perth, Western Australia