Posted on 01/14/2018 8:11:58 AM PST by Tolerance Sucks Rocks
A crack that closed the Delaware River Bridge between Philadelphia and New Jersey last January has prompted the Pennsylvania Department of Transportation to plan repairs to 13 other bridges across the state.
The crack in welding material, which created a 2-inch gap in a major truss, was so serious that officials thought they might have to permanently close the span owned by the Pennsylvania and New Jersey turnpikes. As a result of that problem, PennDOT looked for similar issues in other bridges; the repairs will involve drilling out areas where welding occurred to fill improperly drilled holes, called plug welding, and installing bolts to eliminate the potential for cracking at weld sites.
The practice of filling holes drilled in the wrong place to salvage a piece of steel, common in construction projects decades ago, is no longer permitted in high-tension situations because heating the steel for welding can create a weakness that results in cracking.
Lou Ruzzi, PennDOTs bridge engineer for Allegheny, Beaver and Lawrence counties, said engineers inspected 13 bridges that have steel pieces with plug welds. They didnt find any problems, but the agency will issue a contract in April to drill out more than 650 plug welds and fill the holes with bolts to eliminate the possibility of cracking in the future.
The bolts wont attach to anything, but putting a bolt through the hole and a nut on the other end will increase the strength of the pieces, experts said. The contract will be issued in April and the work will cost from $1 million to $1.5 million.
We havent found any bridge with any cracks, Mr. Ruzzi said. But we dont want to take that chance, so thats why we will repair them.
(Excerpt) Read more at post-gazette.com ...
How?
$1500 to $2300 per bolt. Good gig if you can get it.
Just my guess. The engineers on this thread will obviously know more than these “experts,” so I will defer to you guys.
If the problem is that weld heating has altered the steel properties, drilling out the weld wouldn’t seem to do much.
If a “splint” could be applied that were of the same order of strength as the original steel that extended beyond the heat damage due to the weld, it seems it to me it might help. But, a washer and nut wouldn’t seem to fit the bill!
Tensile strength, won't help.
Twisting strength, won't help.
Compression strength? maybe.
Sounds like a way to generate a few bucks for the local.
That and a little JB weld should do.
Any weld will not only change the temper of the surrounding metal it can cause stress. The formerly molten metal tries to shrink but is held back by the surrounding material. In some cases the stress is enormous. I used to design and build fixtures for assembling motorcycle frames. They had to be extremely strong to resist “weld pull”. The welding sequence was as much an art as science. A good welder had an eye for tacking and then welding in the proper order. We expected the first few frames out of a new fixture to be junk while he got the feel for it.
Hey I'm just a stupid a$$ former ship-yard welder, who worked on the "SMALL-BOATS," 350 Ft. long, Approx. 80' Ft. wide. It's not the heat so much, as the obvious "POOR WELDS." Took a full year of Welding school, through a local community college, just a little after the earth wakes in California, had numerous different people talk to us about the new earth wake standards for rebuilding of roads (read that as bridges) we're talking a whole lot of welding (i.e. heat) going on. When something is welded, properly, the welded joint is stronger the the adjoining material. Just the simple facts.
For those arm chair welding hero's commenting, I've noticed not one of you has asked "GEE WERE THE WELDS EVER X-RAYED?" I'm guessing you didn't even know that X-Raying welds could be done. In the field, when the guy who does the X-Raying shows up, the welders refer to him / her as the un-employment guy. Why, because, if your welds fail, your FIRED!!!!
I had to weld some VERY BIG PAD-EYE'S onto the Pilot house, so they could lift the pilot house up onto the ship. Eighty feet, from the ground up, then move into place. Oh, it only weighed 120 Metric Tons' so I guess I don't know just what I'm talking about.
Truth? Accuracy?
the only way this could possibly do any good is by compression of a plate on either side of the plate with the hole in it and some friction force along the plate to plate contact that adds some strength to the contained plate. That is very iffy of course.
I’m assuming the PennDOT engineers are not stupid enough to count this for anything and so must assume something is missing from the article.
On the other hand, OklaDOT engineers were stupid enough or someone got big enough kick backs to cut three slots across each paving section in line with the two wheel tracks in each lane, put a rebar in each slot and then epoxy or even just concrete the bars in place. Wala, 12 new leak and fracture points in each slab. If somebody can explain the valid benefits of this apparent boondoggle I’m willing to listen.
Earth Wakes. I see you’ve met my acquaintance Otto Core Wrecked...
I would think welding a patch on both sides of the hole would be more effective
Hmmm, I’ve seen that here. Just noted in passing, didn’t give it much of a thought...
That looks like break from fatigue stress nothing to do with fasteners. Caused by cyclical stress by bumpy road.
Holland tunel has stretches of rough bumpy road surface asking for trouble.
I confess to not having read all this article but it reeks of snake oil to me. For example, every square cornered cut made is a stress riser.
http://www.pavementinteractive.org/dowel-bar-retrofit-construction-practices/
I put this in a similar category to foam insulating the underside of a roof. It is a bandaid for a problem that should not be there in the first place and that is HVAC duct work in the attic. For less money and more effectiveness you can retrofit with a full-up zoned mini-split system and throw away all the stinking duct work.
Foaming the underside of decking not done right in most climate zones just creates new problems.
Interesting link, covers everything except why you’d bother to do this in the first place!
Good stuff! made in Sulphur Springs, TX
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