Posted on 03/27/2013 9:25:11 AM PDT by NormsRevenge
At least 30 of the giant bolts that hold together the new, $6.4 billion eastern span of the Bay Bridge have snapped.
As a result, Caltrans is considering replacing all 288 of the bolts on the new bridge before it opens, The Chronicle has learned.
Caltrans insists the new span is safe and that plans to open it the day after Labor Day are still on track.
However, officials say it's too early to determine how long it will take to fix the problem - or the cost.
Toll Bridge Program Manager Tony Anziano said engineers are "pretty confident" the problem with the bolts is not a design issue or a construction problem but related to the quality of the steel bolts themselves.
"This isn't exotic - this isn't some wild issue," Anziano said.
Unlike the Chinese-built deck sections, the bolts - some as long 17 as feet - were produced in the United States.
"It appears to be a type of materials problem - the presence of hydrogen in the metal," he said. The hydrogen makes the metal brittle.
(Excerpt) Read more at sfgate.com ...
This bridge is supposed to take an 8.5 or such.. we'll see soon enough if the Ring of Fire pops one off here..
These seventeen foot long bolts were NOT tested prior to installation?
What’s that smell I smell?
I once met a guy who sold nuts and bolts.
We discussed them for maybe a couple of hours. The markings, quality, the ones used for extreme duty etc. Far more interesting than one might think.
Unfortunately that was over 40 years ago and I don’t remember much. I do remember he said there are a lot of injuries caused by people replacing the nut which holds lawn mower blades on. He said they sometimes just use mild steel nuts or bolts or whatever they are.
the bolts - some as long 17 as feet - were produced in the United States.
"It appears to be a type of materials problem - the presence of hydrogen in the metal," he said. The hydrogen makes the metal brittle.
I'm curious what is the origin of steel that went into those bolts? Does the "produced in the US" tag only mean that they were machined here?
Recall that government presumes that it is competent to command a monopoly on bridge certification and inspection. If a private company had this gross failure of inspection and maintenance, the very same government officials would be rushing in front of the cameras to denounce this laxity and to tell the public how government is protecting them.
Doesn't seem very concerned, does he? Why can't they do their QC and test the parts before installation. Disclaimer- I am no engineer.
Ban fat lesbian crossings.
Pretty confident. Those are words I don't want to hear about any building, bridge, or aircraft.
It seems like everything made today is crap and things made a long time ago are light years ahead.
I believe Kiewit (used to be Peter Kiewit & Sons) is the builder. They are also the ones making the pontoons for the new Lake Washington floating bridge, which are a mess. Leaking, rebar rusting, rebar mislocated or missing completely, and the state is making excuses for them and wasting our money, not to mention the safety of those who will be driving on this bridge.
That information alone made FR worth reading today.
Sounds like a possible engineering problem and the amount of torque used when installing the bolts.
The S.A.E. has ratings on bolts, and it seems the engineering for the bridge should have allowed for worst case conditions -- not best case conditions.
In the 1970's, I worked for a computer company (Microdata) that built a computer based on best case conditions for circuits. It did not account for slow parts.
Of course, semiconductor devices were just started to be used for memories as well as other devices.
The original 1K MOS memories were terrible devices that came out of Silicon Valley then...
You *never* buy 200+ 18' bolts without specifying their performance. Each bolt probably costs more than $10K, so it's a multi-million contract.
Here is the machine that you use for testing metals for strength. This is just a well instrumented hydraulic press, backward. Samples of special shape are made, and then the machine pulls on them, accurately recording the tension and the deformation. This gives you the stress–strain curve. Eventually the sample breaks.
Even if the company that made bolts doesn't have such a machine, it would be sheer insanity to buy a hundred tons of steel without sending a sample to an independent lab for these tests. You would want a chemical and a crystallographic analysis in addition to that. This is what the engineers did after the bolts failed; that's why they are telling us that the steel was wrong (not the right type, or the right type made incorrectly.)
Now the manufacturer of those bolts is going to lose their shirt on this deal. I'm sure their profit margin is not fat enough to cover redoing all bolts and still staying in black.
“I’m pretty sure this gun isn’t loaded.”
“I think your parachute is packed right.”
“I’m pretty sure I got all the sponges out of your body cavity.”
“Almost positive there’s enough cash to cover the check.”
Where have all the adults gone? Is there really a Galt’s Gulch?
That I didn’t get an invite means I better step up my own game.
They came loose because they were elongating beyond elastic limits or even breaking under tension.
Defective parts or defective design? More stress on the bolts than the engineer predicted?
Apparently, they had concrete deck sections MADE IN CHINA that has caused quite a bit of trouble in the 10 year history of this bridge.
Cheap things from China is also a serious problem in this bridge: concrete sections fabricated in China caused considerable delay in the 10 year history of attempting to get the bridge built.
In fact, according to the article, it sounds like trying to save money having the concrete deck sections MADE IN CHINA has probably cost more money in the long run than doing it right in the United States.
This is not even the stress of an earthquake causing these problems, and as someone mentioned, the bridge is supposed to withstand an 8.5 magnitude quake...
>> Sounds like a possible engineering problem and the amount of torque used when installing the bolts.
Or unexpected forces on the assembly.
How does one accurately torque an 18’ bolt?
He is right in a sense- you build and you test.
Usually you end up confirming your design is OK, but occasionally you find an issue like this.
That is why you test.
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