welding concerns for an exp joint continuous cover plate

Date 01-22-2014 18:30

Situation: Large warehouse on the MS gulf coast [i.e. salt water environment] with concrete floor with nominal one-inch wide expansion joints. These joints are to have continuous embedded angles on each side, say L3x3's. Both embedded angles will be 'recessed' below the finish floor, the same thickness as the continuous cover plate. The primary floor traffic is a pnuematic-tired forklift with max axle loads of about 32,000 lbs [or, about 8,000 lbs per tire].

Say the cover plate is 1/4" thick for starters. On one side I want to field-weld via slot welds, say at about 12" c/c, to the embed angle. [Weld only on one side of the joint to permit movement of the cover plate over the opposite embed angle.] Due to the salt environs, all joint steel will be HDG. It's possible it could end up being SS. My concerns:

1a. Is there potential for curling of this plate so that it sticks up [even if slightly] above the finish floor?
1b. If so, should the plate be thicker, or should a different weld 'pattern' be done, or should we abandon welding altogether and go with a screw-fastener type anchorage?
2a. If curling/warping is NOT a problem, either thru 1a or 1b, do you think these welds will hold sufficiently under this forklift traffic?
2b. Do you have any first- or second-hand experience with a similar joint construction in a heavy warehouse?
3. If HDG is the finish, how durable is galvanize touch-up?
4. If SS is to be welded, what does this finish [at the weld area, haz, etc.] look like as compared to the adjacent un-welded areas?
:confused:

By 803056

Date 01-23-2014 15:23

If the warehouse in on the waterfront, I would suggest stainless angles as well as stainless plates over the expansion join. The reason: dissimilar metals corrode rather quickly when in a wet environment with chlorides. Galvanic corrosion is the end result.

Distortion is inversely proportional to the square of the thickness, so a 1/2 inch thick plate will distort 1/4 that of a 1/4 inch thick plate assuming all else is the same.

Angular distortion is nearly proportional to the number of weld beads/weld size. A three pass (multipass) fillet weld will have nearly 2 1/2 times the angular distortion when compared to the same size weld deposited as a single pass. Large single pass welds will cause less distortion than the same size weld deposited with several small welded beads.

Buckling is proportional to the square of the distance between adjacent welds. Reducing the distance between adjacent slots will reduce the bowing of the plate. Welds on six inch centers are better than larger welds on 12 inch centers.

Slot welds provide better access for fusion in the root of the joint when compared to a plug weld. Do not extend the weld to the edge of the angle. Utilize a hold back as per AWS D1.1.

That's the best I have.

Al

By hburg rocket (*)

Date 02-04-2014 21:55

Great info, Al. I have an old DOT detail that shows plug welds with a 1/2" cover plate, but I was leaning towards the slot welds. Someone else suggested ss, too.

I'll do both ss and slots.

thx!