Intermittent full pen welds versus intermittent fillet welds 3

[bridgebuster]

I'd like to know the difference between the two. To be more specific, one of my clients (a state DOT) prohibits the use of intermittent full pen welds but allows intermittent fillet welds. I'm failing to see the logic. For example if one were to fabricate a "Tee" or "L" shaped member with either procedure the result would still be the same: a discontinuity, which could be considered a built in crack.

I'd appreciate any thoughts. It's not related to anything I'm working on. I just noticed this provision while looking for something else but it made me wonder. Thanks

 

[CWIC]

bridegbuster:
Intermittent groove welds are difficult to obtain a sound weld initiation and termination, particularly for multi-pass welds. Intermittent groove welds are prohibited in the AWS D1.1:2000, 2.27.3.

Intermittent groove welds do not perform well when subject cyclic loading as noted in the commentary which further explains why a bridge owner prohibits these as well.

Several years ago one RDP specified intermittent groove welds for some trusses on a project, I made the call and rejected these. The owner's rep., GC, architect and owners inspector all agreed any welds "prohibited" by the code were unaccepatble and repairs had to be made.

 

[ryan1060]

In order to produce quality groove welds were more than one pass is required to fill groove, run out tabs with similar cross sectional shape and or a backing bar extension (depending on weld geometry requirements) are added. This allows the welder to start and stop his arc outside of critical areas. The defects associated with the stops and starts are then removed when the run out tabs and backing bar extensions are removed later in the process.
Theoretically, if you can produce a fillet weld with a perfect start and stop than you should also be able to produce numerous split layered technique individual passes. However, real life has a way of preventing this. There are numerous reasons for this: geometric problems manipulating the electrode, welding position, joint restraint, material weldability, material crack susceptibility, and finally but not least production pressures.
Regards,

Aubrey