Standard Weld Details and Galvanizing

[dozer]

AISC is quite specific about not welding across the beam web thickness when attaching a shear end-plate. See AISC 13th ed., page 10-49. Other types of shear connections have similar requirements that prohibit complete welding. It's not uncommon at all to have a beam with a shear end-plate that gets galvanized. "Common" knowledge among most fabricators is that things that get galvanized get completely seal welded so the acid or whatever doesn't get in cracks. So AISC is telling us one thing and the fabricator another. Who is right? Surely the folks that wrote the AISC code realized that a goodly portion of fabricated steel is going to get dunked in a vat of molten zinc, so I'm thinking they wrote exactly what they meant and this seal welding idea isn't really valid. Of course, I could be completely wrong, in which case what's a feller to do?

Don't get to hung up on shear end-plates, that's just what I happened to be working on so I used that as an example. Shoot, look at double angles welded to the end of beams as a shear connection. Again, AISC says welding across the entire top of the angle must be avoided as it would inhibit the flexibility. It doesn't say unless beam assembly is to be galvanized.

By the by, I know somebody is going to say something like you seal weld and a seal weld is not a structural weld. I'm not buying that. First, just exactly what size is a seal weld? Is this seal weld so flexible it will allow the beam to rotate but not crack the weld?

Anyway I sure would like to know the straight skinny on this. Thanks.

 

[ToadJones]

Are you worried about the pickling liquid getting into the interstitial space between plies of steel?
If so, what is the concern there?

 

[dozer]

No, I'm not concerned about it (should I be?). I'm saying everyone I've ever met with a welding gun in his hand says you have to completely weld every seam on something that is going to be galvanized. I'm just asking is that true and if so, then how can one make shear type connections that allow flexible enough to allow rotation.

I must admit, it does make sense that having "cracks" that the pickling liquid could get into and possibly trapped there by the galvanizing would be a bad thing. The stories I've heard is it leads to corrosion from the inside. Hey, I'm just reporting the news.

 

[hokie66]

Large overlapping surfaces have to be avoided or vented for safety during galvanizing. If in doubt as to a given detail, contact a galvanizer in your area.

http://www.gaa.com.au/uploads/Wall Chart.pdf

 

[SAIL3]

I typically put a seal weld all-round....seal weld does not have to be a structural weld unless required by the loading....if one does not seal, then over time rust can develop between the plies as there is no guarantee that the galvanizing liquid will effective migrate in there....

 

[gtaw]

I guess the trick is for the detailer to think ahead and select details that are conducive to good galvanizing practices. The detailer has several types of connection details to select from. If all else fails, a short conference call between the detailer, Engineer, and the galvanizer can result in a "best practices solution."

Best regards - Al

 

[dozer]

Thanks for the feedback. I've been reading up on this since I posted and I even contacted AISC. There is no pat answer but it seems if the joint won't be experiencing much rotation (I know, I know, what is "much rotation") then seal welding is the way to go for reasons mentioned. Thanks again.