Retrofitting Existing Eeld Defects in a Bridge Plate Girder

By bp158 Date 10-23-2008 17:12

I am looking at ways to retrofit weld defects in bridge plate girders. The girder material is A36 steel, with Charpy V-notch values ranging from 4.6 to 33 ft. lbs tested in accordance with AASHTO 1987 (samples tested at 20 ft. lbs @ 20 degrees F). A large number of samples failed the Charpy test. Existing flange to web connection is made with a single pass 5/16" fillet weld. There are many areas in the tension region where the diaphgragm connection plate and transverse stiffener weld intersect with the flange/web weld. Also, there are areas where there is evidence of miltiple weld pass in the flange /web weld. Some weld areas have perosity and weld splatter.

I think one way to retrofit this weld defect is to grind the defective area and reweld. Does anybody have any experience or thoughts on dealing with this kind of a problem?

By 803056

Date 10-24-2008 00:56

I think this is the time to consider retaining the services of a qualified professional engineer that is experienced in welding engineering.

Best regards - Al

By RBeldyk (**)

Date 10-24-2008 01:26

Do some research on "triaxial stress" and a second search on the "Hoan Bridge"

By HgTX

Date 11-04-2008 23:35

"multiple weld pass" is not in itself a defect.

Diaphragm connection plate welds crossing the web-to-flange weld is not inherently a problem; the problem areas on the Hoan bridge had much more complex geometry and stresses than that. Intersecting welds are discouraged but are not always automatically a problem (for example, every web-to-flange weld intersects the web and flange butt splices). This particular form of intersecting weld is common in Japan (http://international.fhwa.dot.gov/Pdfs/SteelBridge1.pdf) and there is research in the U.S. suggesting it would not be a problem (http://www.utexas.edu/research/ctr/pdf_reports/0_4178_1.pdf). You'll have to have a design engineer evaluate the state of stress at that intersection. If it's not a problem, you could make a worse mess by trying to remedy it.

Spatter is not a weld defect. It can cause a problem with paint and should be ground off before you repaint the bridge, but it's not a weld defect.

Porosity, if at a rejectable level (check AWS D1.5 for acceptance criteria), would be repaired in exactly the same way it would have been in the shop, by grinding and re-welding.

I'm not sure what you're saying about the Charpy results. Is it the base metal or the weld metal that's failing? What retrofit are you proposing there?