corroded steel beam 2

[jdr08]

Hi,
I observed a moist crawlspace where the main steel beam was corroding and need to provide a repair. The steel beam is a W16x31. The corrosion was fairly minor but there was some loss of section. Obviously, they need to take care of the cause and get the moisture out. But for the beam, would an appropriate repair be to just scrape off the corroded product and stitch weld 1/4" plates to the flanges and webs, replacing much more than the thickness of the lost section?
Any suggestions would be very appreciated.
Thanks,

 

[JAE]

You might first do some calculations to see if the beam, with the section loss as-is, would work under the applied loadings.

If it can do OK as-is, then clean the beam, re-paint, and then get the moisture out of there.

If it can't perform, then yes, adding plates would be an option. Adding supports or cross beams to shorten the span is an option sometimes.

You don't always have to splice on new plates exactly where the corrosion occurred on the section. For example, if you top flange is reduced by corrosion, you could possibly add a bottom flange cover plate across the span to increase the overall section properties and live with a reduced top flange. You'd still have to check the top flange local buckling, etc. with the reduced thicknesses.

 

[dik]

This might help...

Dik

 

[JAE]

dik,

So you enter a uniform depth of corrosion and the calculate new properties, load capacity, etc.?

Looks like a good idea. One question would be what if your corrosion was confined to just one flange, or one web?

 

[JedClampett]

If you're doing any welding, you probably want to shore the beam. It will remove the existing stress from the beam and you won't run the risk of the heat from welding reducing the stiffness and causing additional deflection.

 

[dik]

Thanks, Jeff:
My application was for a mine and corrosion was 'nearly' uniform all around.

The original spreadsheet was developed for corrosion of a structural T with a plate welded to it and the corrosion was limited to the T and the inside face of the steel plate. I then modified it for the mine project. The info is there, it's easily modified it to suit the need. Sometimes a little corrosion has little effect on the overall section properties.

Since I've started my latest job, most of the stuff I'm doing is different than anything I've ever done... I do all my programming at home and not charged to the project; this way, I retain ownership of the work. I post the sheets, however, to the other engineers in the office for their use (I'm a great believer in sharing info).

Dik

 

[jdr08]

Thanks everyone for the advise.
Jed- I ended up recommending the beam be jacked up at 3' o.c. to result in a straight line between supports and relieve its stress.