

What's Going on at the Bay Bridge - soundsop
http://www.sci-experiments.com/BrokenBridge/BrokenBridge.html

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antonovka
The engineering issues are very interesting, but I find the social issues even
more intriguing. What would happen if the bay bridge only re-opened to
commercial traffic, and BART service was radically increased?

The bridge carries 280,000 thousand cars daily -- that's a _lot_ of traffic
driving around our city, people eating at restaurants, etc. Could we maintain
that level of commerce while relying almost solely on public transportation?

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hack_edu
Yes, and no. Certain areas of the city and Oakland would become further
gentrified. There's a large demographic of folk who are happy riding BART but
won't get on a bus or Muni.

How has car traffic been in SF this week without the bridge?

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yosh
Traffic in SOMA is a _lot_ less around evening rush hour, because there isn't
a mess of cars backed up on the streets leading up to the I-80 enterance.

Traffic is _worse_ , however, around the other bridges in the area, since the
interchanges to the major freeways (101, 880) at those bridges do not have the
capacity to handle the offload from the bay bridge traffic. Some of those
interchanges only have one lane vs. multiple for the bay bridge entry and exit
points, and not enough merge distance to make things smooth.

Parking at most BART stations is also pretty much at capacity, whereas usually
there is plenty of empty spaces.

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ars
It seems to me that the eyebar was not designed correctly - it has a stress
concentration point exactly where it cracked. (If you can visualize the forces
acting on it, and then take the derivative you'll see the inflection point.
It's important that the derivative of the forces be smooth.)

If I were making one, I'd make it in a tear shape. i.e. the shape you would
get if you wrapped a rope halfway around a bar and pulled on it.

Interestingly the outside of the eyebar is (almost) the right shape. Someone
filled in the inside to make it a circle. This is a mistake - the skin of
metal is much stronger than the inside (that's one of the reasons cables are
made of many many strands). By filling it in you are not making it stronger -
you make it weaker, because now you have less skin on the inside, and
additionally you have a stress concentration point.

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NikkiA
The bay bridge was started in 1933, and construction ended in 1936. Metal
fatigue and many other aspects of material science were unknown at that time.
If the eyebar was original, or built to original specs, it's entirely possible
that the failure mode it exhibited wasn't even predictable given 1930s
knowledge of materials under stress.

So I'm not in too much of a rush to find someone to blame :)

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mechanical_fish
I should probably enforce a limit on the number of times I'm allowed to plug
this book on HN every year: J.E. Gordon's _Structures, Or Why Things Don't
Fall Down_

[http://www.amazon.com/Structures-Things-Dont-Fall-
Down/dp/03...](http://www.amazon.com/Structures-Things-Dont-Fall-
Down/dp/0306812835)

It's not exactly a _young_ book, but it's newer than the Bay Bridge...

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billswift
This is less technical and more readable, [http://www.amazon.com/Engineer-
Human-Failure-Successful-Desi...](http://www.amazon.com/Engineer-Human-
Failure-Successful-
Design/dp/0679734163/ref=sr_1_1?ie=UTF8&s=books&qid=1257031893&sr=8-1) , and
Petroski describes a bridge that failed as the result of a single eyebeam
failure. In that case though, there were only 4 very short eyebeams supporting
the roadbed, one at each corner. He didn't actually call them eyebeams, but
hangers, but from the photos, they are the same thing.

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jamesbressi
So why hasn't the news contacted this guy and borrowed him for their
reporting, or is journalism dead? Or was I just being sarcastic (about
journalism being dead that is)?

Furthermore, I hate our lawsuit happy society, but someone needs to be held
accountable.

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dotBen
From what I understand the guy who wrote this has some connections with the
contractors who are doing the work... point is, he's probably not supposed to
have written this (despite it being a public bridge, public property, state
tax-funded project).

~~~
mmt
I'm routinely startled by how little "sunshine" we have even on such high-
profile projects.

Even information about the peripheral closures arouses my suspicion, rather
than satisfying my curiosity.[1]

[1] I asked why I-80 was closed between 7th and 4th St exits (the latter being
the last pre-bridge exit, which I use in my commute) and why the western span
is closed at all, expecting a response referencing additional serendipitous
work or inspection. Instead, Caltrans's public information officer Bart Nay
replied in email "The closures you are referring to at 7th and 4th Streets are
necessary to prevent vehicles from approaching the closed Bay Bridge." That
just made me wonder "and what might we find out if we _were_ allowed to
'approach'?"

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anigbrowl
That was a hell of a lot more informative than anything else I've read/watched
in the last week.

~~~
hop
Yeah, the author put a lot of work into this.

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cma
And Murdoch wants to start charging for their basically non-existant
"coverage" of stuff like this...

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kqr2
Here's a nice pdf of the enhancements to the eyebar repairs:

[http://baybridgeinfo.org/sites/default/files/pdfs/eyebar_rep...](http://baybridgeinfo.org/sites/default/files/pdfs/eyebar_repair_web.pdf)

