huangyhg

bent column flange
hi,
we have a piece of machinery that has been overloaded and fittings torn out of a 210uc, in doing so a section of the column looks a bit like this - if u use your imagination
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this is over a small region, entire section is about 1500m long and this bending is limited to about 300mm. the flange has bent back about 20-30mm and stretched a little bit.
one option is to press the bent parts back into shape with mobile hydraulic jack, obviously this will cold work the material (grade 350 incidently), or apply heat to help then quench.
option two is to cut away the bent section of flange leaving a 't' shape:
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| then welding a plate to replace the flange with full penetration sp welds.
or third option is to cut out the bent section completely and weld a new piece of uc.
the aim is to try and restore the column to original strength (am i dreaming?).
what are things i should take into account with welding and/or cold working? both of which i assume will reduce strength of the column no matter what i do? any comments appreciated.
dave

useing heat or trying to bend the flange bach to a straight vertical shape does not appear to be practable, especially if the column is under load. cuting out the bent portion and replacing with a new plate with full penetration welds seems the most practable way to make the repair. you would achieve full column stregth back. i am not familiar with your steel grade but i assume it is weldable. make sure you shore the existing loads on the column before you attempt a repair.
hi ffield,
thanks for your input - your first comment on bending flange back as "...not being practable..." - could in this case be carried out, the column is under no load when this piece of equipment is not functioning. the column makes part of a trussed frame in the vertical.
but i would tend to agree that welding a new section in would assure that the column is damn close to its original shape.
incidently grade 350 has minimum yield of 350mpa and is readily welded - similar i think to astm a573-450)
dave
i agree with ffield.
a repair method i have used several times for columns with badly corroded flanges (so corroded that it hasn't been practicable to weld strengthening elements to the flanges) is to weld beam tees (ie. half an i-beam) to the column web to make a cruciform section. this essentially transposes the major and minor axes. in each case the columns were in braced frames where the major and minor axis effective lengths were similar and were subject to axial compression and only small bending moments due to secondary effects.

of course this method of repair is not suited to columns with significant major-axis bending moments or columns where the major-axis effective length is much longer than the minor-axis effective length.

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