"welding occurred to fill improperly drilled holes"guess who i'd be sending the bills to...
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, PennDOT’s bridge engineer for Allegheny, Beaver and Lawrence counties, said engineers inspected 13 bridges that have steel pieces with plug welds. They didn’t 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 won’t 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 haven’t found any bridge with any cracks,” Mr. Ruzzi said. “But we don’t want to take that chance, so that’s why we will repair them.”
(Excerpt) Read more at post-gazette.com ...
Bring in “That Man Bolt” to do the repairs.
I was waiting for one of the Pros on FR to comment on this. I’m no Rocket Engineer but at minimum I would think that a REAL fix would involve a plate on each side extending well past the “problem area” with 4 or 5 bolts on each end.
"welding occurred to fill improperly drilled holes"guess who i'd be sending the bills to...
Oh C’mon! Welding is no different from painting! If you watch someone doing it for a few minutes you can easily do it too. /S
“I don’t understand how putting a bolt through the hole strengthens the piece of steel that the hole is in.”
The heat only weakens the surrounding area, the bolt/washer combo probably extends into the unaffected area.
Remember, this is for tension stress only. Take a piece of 30 mil shower liner (i.e., thick rubber matting) that’s 6” x 6”, drill a half inch hole through the center (if you can without tear it), then grab two sides and pull apart. The liner is very weak at the hole. Then put a half in bolt through it with washers on both sides and secure it tightly with a nut. Then try to pull it apart...much tougher - because you not only lose the advantage of the hole in helping to pull it apart, you now have a section between the washers that won’t even flex. The result is a stronger piece of 6 mil. (you have to ignore gravity in my example, as it doesn’t apply in the case of bridges).
Pretty clever fix, in my opinion.
“I’m no Rocket Engineer but at minimum I would think that a REAL fix would involve a plate on each side extending well past the “problem area” with 4 or 5 bolts on each end.”
Sounds like a fix, but perhaps it’s overkill when a single bolt plus washers would work.
No doubt!
The 1 bolt plan will not PROPERLY fix the problem.
I don’t understand how putting a bolt through the hole strengthens the piece of steel that the hole is in.
If the heat from the weld plug has already weakened the steel it seems that the damage is already done.
= = =
My first thoughts, too.
Maybe ... If they drill out past the heat affected zone, and put in a bolt to fill the new hole (and treat for corrosion resistance,etc.) ...
but now we have removed material (area) that may increase the stress, as in stress = load / area.
So, I need more data.
OR, because the Govt. is involved,
Drilling something and putting a bolt in could be called Screwing it.
“Bridge is all OK now, we Screwed it up.”
“The 1 bolt plan will not PROPERLY fix the problem.”
I’m not an engineer, so I can’t say I’ve done the stress analysis for thee cases to know either way - but one would think that others have.
As it is, I was just explaining the concept - not stating whether it would work in a particular application.
This reminds me of a story my dad told of a lady driving a Model A. She stopped at a filling station and the attendant noticed a crack on one of her fenders. He told her he could stop the crack from going any further if she would like. She said please do. He goes in and gets a brace and bit and drills a hole right at the end of the crack. She looks on with a perplexed look. She asks what that does. He tells her the crack goes into the hole and having no where to get started again stops right there. She says “ I’ll be damned, I always wondered what my belly button was for”.
nope...
Couldn’t they bolt on light, high-strength metal plates made of titanium to add structural support without too much weight?
What I got out of it is that this as much an art as it is a science, and the textbook answers sometimes mysteriously just don't fit reality. We ought to be giving the guys who try to get this right, the benefit of the doubt.
We could use a few in the House and Senate....
This is why we never check our own work...
What you did there, I see it.
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