A722 Threaded Rods

[bridgebuster]

I'm trying to help out a colleague regarding the use of A722 threaded rods, galvanized.

A contractor on a seawall project is proposing a design change. The original design of the sea wall consisted of precast panels bolted to cast-in-place concrete pier caps; the bolts were 7/8” A325, galvanized. The end of the pier caps mushrooms out to serve as a shear block. The contractor proposes to eliminate the concrete shear block and as a result needs a huge increase in bolts – number and diameter. A couple of questions:

Can A722 be galvanized? I did a search and found nothing conclusive. Dwyidag recommends reducing the allowable strength by 5% when using galvanized A722.

These rods will be used in slip critical connections. What is minimum pre-tension? Equating A722 to A490, a 1" diameter bolt would require a 73 K pretension.

Is A722 suitable in a marine environment; these rods would be constantly wet?

Thanks

 

[EdStainless]

I am not going to give you any hard engineering data, call this a gut check.
You want to support constant load in a seawater application, I would use the concrete.
The trouble with galv bolting is that you need clearnace for the galv, so the tread fit isn't as tight. You also have to look at potential failure modes. What may happen years out.... I don't think that I want to trust steel bolts, under load, in seawater, for a long time.

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[Screwman]

I agree with Ed. I see all sorts off problems down the road relating to the corrosion that will certainly occur in the studs. I would not count on a galvanized bolt to long-term load carrying in a marine environment. Use the caps.