Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Backer bar removal

[Subject Prev][Subject Next][Thread Prev][Thread Next]
I have been asked to look at three OMF that were installed as part of a voluntary seismic upgrade. Aside from the occasional OMF, I don't do much welded steel design, so I'm being guided by my reading of FEMA 353. These frames don't carry any vertical load, but the 3 story building is located in the S.F. Marina so the ground motion could be fairly serious some day. Using the Soils Engineer's design criteria, the frames look to be loaded to about 50% of their capacity (ASD).

W10x19 beams and columns, all the welds are CJP groove welds, and the backing bars were left in place. The "defect" in question is a small misalignment (.25" max.) between the centerline of the .395" thick column flanges and some of the .5" wide web stiffeners. My inclination is to not worry about the misalignment; at the column flange/beam flange joints remove the backer bars, back gouge, and fillet weld; and add a fillet weld between the backer bars and the beam. Per the comments in FEMA 353 I would not weld the stiffeners to the backer bar.

Am I concerned about & repairing the right things?
What sort of tolerance is reasonable for continuity plate alignment?
How important is the removal of backing bars in these relatively thin sections (my standard notes say to always remove them at all CJP weld locations)?
Why does FEMA 353 say to not fillet weld the backer to the stiffener?
Access is really difficult is a couple of locations. How serious a problem would it be if my recommendations were applied asymmetrically?

Chuck Utzman, P.E.

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at:
* * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to:
* Questions to seaint-ad(--nospam--at) Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: ******* ****** ****** ****** ******* ****** ****** ********