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OT: Cracked steel beams found in San Francisco 2.2$ Billion transit center

Living in Chicago and having worked on infrastructure 100 plus years old I have to question how in this day and age these things happen. Lake Street bridge was built in 1916 and still operates. Still has elevated trains running on the upper level and street traffic on the main level, buses cement trucks etc. Yes some structural ironwork has been replaced be of corrosion but the original machinery is still performing. Some of these bridges in Chicago are older than that.
 
Usually welded beams have internal stresses in them due to the nature of being welded.
never heard about annealing welds after as it is a lot of metal to heat up to do so.
If it was MIG welded you can get underbead cracking and it shows up straight away, for large beams here they use submerged arc here as the amount of metal that can be deposited is higher it goes on at a higher rate.
Be good if there was more detail listed on how it cracked.
Bending moments on beams result in shear forces in the web being created, was the web too thin if it cracked in the web could be a question to ask, that more a design issue then fabricating one.
 
Street said:
Usually welded beams have internal stresses in them due to the nature of being welded.
never heard about annealing welds after as it is a lot of metal to heat up to do so.
Click to expand...

It's called post-weld heat treatment (PWHT). The temperature is 400-500 degF lower than you use for annealing. It also makes weldments significantly more stable for machining.

Interestingly, AWS D1.1 has rules for how to do PWHT, but it does not have rules as to when it is required, even on thick pre-qualified joints. The BPVC, on the other hand, requires it for >1.5" thick, and sometimes >1.25" thick.
 
The same engineer said that normally he would expect to see truss beams in this size so any failure would be limited to one portion and stay within safety margin. He thought the beam maker was not used to making stuff this big and annealing would not be a big deal for smaller stuff. They were really out of their league. Pieces made in at least four different locations and shipped back and forth so they may have thought the other shops took care of that treatment, that is not normally done in this shop.
I bet heat treatment needs a big oven for a 6.5 x65 beam, and no one had one big enough so the passed the buck to the next shop that they thought had a big enough oven. The steel was made in the USA. In China they might have issued a certificate that it was heat treated to make the customer happy.
Bil lD
 
Last edited:
Bill D said:
The same engineer said that normally he would expect to see truss beams in this size so any failure would be limited to one portion and stay within safety margin. He thought the beam maker was not used to making stuff this big and annealing would not be a big deal for smaller stuff. They were really out of their league. Pieces made in at least four different locations and shipped back and forth so they may have thought the other shops took care of that treatment, that is not normally done in this shop.
I bet heat treatment needs a big oven for a 6.5 x65 beam, and no one had one big enough so the passed the buck to the next shop that they thought had a big enough oven. The steel was made in the USA. In China they might have issued a certificate that it was heat treated to make the customer happy.
Bil lD
Click to expand...

Yup, I was looking at a weldment of 2 3/4" thick steel, subarc welded
with 3/8" wire at about 1500 amps. Then flip over, and Air arc out the root and weld the other side. Puddle is about 2" wide and 3" long.

Done for many years, good running, proven process.

Has now been farmed out to lowest bidder in China.

Looks to be welded vertical up with 1/8" stick electrodes, many passes.
Still, should be acceptable substitute eh ?

Nope, holes machined thru weld (normal part of making the part) showed
extreme porosity.

No one is doing x-ray on the incoming, even a few parts.

Why would you ? The in house ones never needed it, proper machined
weld chamfers, root control, run-off tabs, voltage & current controlled
too. Complete process controls in place.

Not just everybody has the resources and powerline to run a 1500 amp subarc
machine.

Apparently the chinese low cost bidder has a Lincoln 225 in a 2 car garage.....:skep:
 
Wow that is scary. I am glad they caught this. I could see moving the beam from one place to another would invite mistakes. Yet someone had to sign off each step in the process. Add shift change also to miscommunication.

That Korean dude filling in six inches of a gap with sticks is pretty scary. In America there are guys who know that is wrong and will quit rather than follow a bosses order to “ just fix it” screaming to the top of his voice.
 
digger doug said:
Yup, I was looking at a weldment of 2 3/4" thick steel, subarc welded
with 3/8" wire at about 1500 amps. Then flip over, and Air arc out the root and weld the other side. Puddle is about 2" wide and 3" long.

Done for many years, good running, proven process.

Has now been farmed out to lowest bidder in China.

Looks to be welded vertical up with 1/8" stick electrodes, many passes.
Still, should be acceptable substitute eh ?

Nope, holes machined thru weld (normal part of making the part) showed
extreme porosity.

No one is doing x-ray on the incoming, even a few parts.

Why would you ? The in house ones never needed it, proper machined
weld chamfers, root control, run-off tabs, voltage & current controlled
too. Complete process controls in place.

Not just everybody has the resources and powerline to run a 1500 amp subarc
machine.

Apparently the chinese low cost bidder has a Lincoln 225 in a 2 car garage.....:skep:
Click to expand...

I think it is a Miller Thunderbolt...:D
 
Poor management along with trading profits for safe infrastructure.
Frankly, the federal government could build a factory for all this sort of thing and do a better job than the private sector these days.
We could call it a matter of national security and it would be closer to true than steel and aluminum tariffs.
 
Spinit said:
Wow that is scary. I am glad they caught this. I could see moving the beam from one place to another would invite mistakes. Yet someone had to sign off each step in the process. Add shift change also to miscommunication.

That Korean dude filling in six inches of a gap with sticks is pretty scary. In America there are guys who know that is wrong and will quit rather than follow a bosses order to “ just fix it” screaming to the top of his voice.
Click to expand...
And plenty of guys that will just do what the boss says because they have bills to pay too.
 
Seems to me induction hearing combined with a sand bed slow cool would be an effective way to anneal long sections without having to need a 100’ long oven.
 
john.k said:
Saw a program about South Korea s top welder.......apparently called in when ship plates dont fit.....he was filling a 6 inch wide gap with a stick welder.
Click to expand...

"Gap-O-Sis"
"Gap-I-tis"
"Tight enough to hold bailed hay"

I find it easier to fill in with solid wire MIG.
 
Spinit said:
...filling in six inches of a gap with sticks is pretty scary. In America there are guys who know that is wrong and will quit rather than follow a bosses order to “ just fix it” screaming to the top of his voice.
Click to expand...

Or not. Back when I did warranty repair welding on Case and Hein-Werner earthmoving machines I had to go to the dealer to fix a bucket with its wear liner peeling away from the front lip. I started in gouging it out with a torch and uncovered the end of a 3/16 coated electrode which had been laid in the weld groove and covered up. That was a challenge, as I didn't think anybody would believe it. I carefully blew around it and removed it intact, with most of its coating still attached. The delighted dealer called the factory and had me describe it. The guy on the other end of the phone knew there was a container of rod that size near where that operation was done and accepted the claim without question. I didn't think to ask whether the shop was union, which might have explained why he seemed to have no interest in confronting anybody about it.

Our local welding supply (this was 45 years ago) had a framed weld X-ray on the wall revealing the perfect outline of a large spud wrench. I think it was from a shipyard but nobody knew when it had been taken.
 
Miguels244 said:
Seems to me that a correctly preheated joint using correct filler could fill a pretty good sized gap well.
Click to expand...

Preheat can actually be your enemy when filling a wide gap.

Here's a first pass on some badly fit pipe. (I'm no pipe welder, but I do the best I can)

I'm directing the heat against the good piece of pipe that hasn't been cut. The idea is to run a pass inside the pipe edge, and try to follow the curve of what will be your finish pass. The weld is actually inside the outside diameter of the angle cut pipe.

gaps1.jpg You're building a tremendous amount of heat as the weld progresses upwards. The puddle will get harder to control as the heat increases in the metal.

One of the next few filler passes, built on, and against, the first pass.


gaps2.jpg This pass has to build out the first pass without destroying the original pass. Sort of like buttering a cake. Again, you do not want excessive heat that a preheat would introduce.

The final result.

gaps3.jpg Some guys might try to fill this gap with a weave. I don't like a weave. It builds excessive heat in the metal. In this case, a weave would likely burn away the edge of the angled pipe, and you'd have a mess. It can be a challenge to fill a gap with stick welding, unless you're using 60xx rod. I run 7018 because I'm just comfortable with it I guess.

Preheat definitely has its place. It's generally used for thicker sections (3/4" plate, or thicker..or highly restrained welds that can crack when cooling)

A guy would have little trouble filling this particular gap with a wire machine because most wire is a fast freeze filler. Wire is easier to weld with, once you set the proper parameters on your machine.
 
digger doug said:
Done for many years, good running, proven process.

Has now been farmed out to lowest bidder in China.
Click to expand...
When they were building the bay bridge in Shanghai, I ran into a few of the inspectors in bars around town. They took to drink :) They had stories. They told their bosses what was going on on a daily basis but the bosses refused to listen.

Then Caltrans paid Carnegie-Mellon to say that cracks didn't matter and that solved the problem.

Maybe the city should have given Carnegie-Mellon another endowment ?
 
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