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1-35W Bridge Collapse Update

Here's video from a security camera that was across the street and captured part of the bridge as it collapsed:

According to a bridge specialist I saw on Fox last night, this bridge was built using the pin and hanger method. Well, in this piece about a bridge in Texas, the pin and hanger method was described at "old."

Innovative techniques in precast concrete bent cap connections are being used by the Texas Department of Transportation as it replaces an antiquated bridge over Lake Belton along State Highway 36 in Bell County.

Groundbreaking for the $20 million project took place in September 2002 to replace the existing bridge that was constructed in the early 1950s. "The existing structure is 45 to 50 years old," said Paul Hoffman, Belton area construction inspector for TxDOT. "It was built using the old pin-and-hanger method, and it's just tired."

I don't know if this method was considered outdated back in 1967 when the bridge was first constructed, but in 2005, inspectors said the 35W bridge structure was insufficient. Here's more information about the bridge:

The National Bridge Inventory contains a report on this bridge from 2003. It reports the following items:

* Deck Condition: Fair.
* Superstructure Condition: Poor.
* Substructure Condition: Satisfactory.
* Scour: Foundations determined to be stable.
* Bridge Railings: Meets currently acceptable standards.
* Structural Evaluation: Meets minimum tolerable limits to be left in place as-is.
* Water Adequacy Evaluation: Superior to present desirable criteria.
* Bridge Sufficiency Rating: 50%

A University of Minnesota Civil Engineer in a report to MN-DOT recently noted that this bridge is considered to be a non-redundant structure. That is, if any one member fails, the entire bridge can collapse. A key factor is that there are only four pylons holding up the arch. Any damage to any one pylon would be catastropic. The textbook example of a non-redundant bridge is the Silver Bridge over the Ohio River. It failed shortly before Christmas in 1967 resulting in 46 deaths. A single piece of hardware failed due to a tiny manufacturing defect. But that piece was non-redundant, and the entire bridge collapsed into the icy river. Today, bridge engineers design bridges so that any single piece of the bridge can fail without causing the entire bridge to collapse. It is tragic that the I-35W bridge was built a few years too early to benefit from that lesson.



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Comments (26)

Here is a good video from a... (Below threshold)
doctorj:

Here is a good video from a safety engineer.
http://kstp.com/article/stories/S156551.shtml?cat=1&v=1

Perhaps some of that pork i... (Below threshold)
Roy:

Perhaps some of that pork in those highway bills isn't such a bad thing after all.

The thing here seems to be ... (Below threshold)
jpm100:

The thing here seems to be that the bridge was built without any submerged footings. This created a long unsupported span that would go all together without a chance of it stopping at a supporting location.

BTW Kim, good post... I wok... (Below threshold)
Paul:

BTW Kim, good post... I woke up and tried Drudge and the two big mane Minn bloggers only to find you had them all beat.

The DailyKos and DU are alr... (Below threshold)
WildWillie:

The DailyKos and DU are already blaming GW for this. How low and pathetic, but expected. You can count on the lefties to spew hate and insensitivity at a time when investigation and compassion are needed. I personally think that the amount of fatalities with this disaster is just a miracle. That had to be horrific to be on that bridge when it collapsed. Just unbelievable. ww

IT IS BUSH'S FAULT FOR THE ... (Below threshold)

IT IS BUSH'S FAULT FOR THE WAR ON TERROR! BUSH LIED, AND NOW MORE PEOPLE DIED! WAAAUUUUGGGHHH!!

*cough*

*hack*

Damn. Sorry. Must have been channeling some idiot liberal still fuming about levees...

DAMN YOU WW! DAMN YOU TO H... (Below threshold)

DAMN YOU WW! DAMN YOU TO HELL!

Bah. :P.

I've read before about anot... (Below threshold)
Cousin Dave Author Profile Page:

I've read before about another pin-and-hanger bridge that collapsed. I think it was in Conneticut in the early '60s. As I recall, one of the observations of the investigation team was that corrosion had occurred in a critical location that was impossible to inspect visually without disassembling the connection.

Note that the girders just ... (Below threshold)
Neo:

Note that the girders just to the right of the top of the chain link fence are already buckling in the first frame of the video.

It looks like the girders on the end of the bottom of the inverted tressel of the center section buckled first (see post above), then the super structure compressed inward causing the entire center section to fail off it supports.

The most scary part is that the section of the bridge in the distance stands for a bit after the center section drops, then it moments later drops as well.

I bet that the initial problem that caused the bridge to collapse with be determined to be an undermining of the support (visible in the video between the two section that collapse) by erosion of the water of the Mississippi.

Also, if you look carefully, there appears to be some puffs below the road deck, showing the compression of the steel below rubbing the concrete above. I bet some of the conspiracy nuts will claim this was part of a "controlled explosion" to bring the bridge down.

This is a tragedy, being Ir... (Below threshold)
Judith:

This is a tragedy, being Irish, however, some quirk makes me think....is this where the big dig people are now located?

Perhaps some of that por... (Below threshold)
J.R.:

Perhaps some of that pork in those highway bills isn't such a bad thing after all.

Yes, throwing more money at a poor design always results in getting a better one. /sarcasm

Roy, care to indulge us with how more money would have stopped this disaster?

Just goes to show what happ... (Below threshold)
FreedomFries:

Just goes to show what happens when Republicans run a state. Everything falls apart.

FF: "Just goes to show what... (Below threshold)
Drago:

FF: "Just goes to show what happens when Republicans run a state. Everything falls apart."

Two words. Say them with me: Detroit. Michigan.

FF,The Minnesota H... (Below threshold)
Robert the Original:

FF,

The Minnesota House is Democratic by at least 30 seats.

Road and bridge funding is a current debate; the Democrats, of course, never have found a tax they don't want to raise.

See Detroit, Michigan again, and the tax death spiral.

FreedomFries, that is among... (Below threshold)

FreedomFries, that is among the more ridiculous of your many ridiculous statements.

Neo, the kind of bridge des... (Below threshold)

Neo, the kind of bridge design in question has no redundancy. A single component failure will take out the entire structure catastrophically. I suspect that we'll find that there was a single support structure pin that failed from a manufacturing defect that went undetected. If that turns out to be the failure, it will not be something that could have been detected by inspection. The reality is that these kinds of designs are long obsolete. What is debatable is whether or not the class of bridge design needs to be replaced short term or whether or not we'll wait until the end of their service lifes to replace them.

Robin Roberts,if you think ... (Below threshold)
FreedomFries:

Robin Roberts,if you think my comment above was intended as serious, it likely explains why you are a Republican and think(?) the way you do.

from this footage it looks ... (Below threshold)

from this footage it looks like it failed off camera on the near side, in other words, you can't see much from this footage. Looks like something happened off camera that caused those trusses to buckle as noted by neo above. as 'interesting' as this footage is, and I'm sure it will be very useful to experts, I don't think the key event is captured on it. It just seems odd to me that the middle collapsing would cause the near side to fall so smoothly and seemingly without resistance...if one piece of one truss went, which could lead to a collapse if all the reports of how there was no redundancy are correct, should lead to a twisting collapse...at least SOME twisting as the other truss held, if only momentarily, since it should have been designed to handle more than 50% of the total load, but instead the near side just drops like a rock straight down. And if the initial problem was near the support, shouldn't it have preceded the smooth collapse of the near side by at least a little? Instead, from frame 0 to frame 1 the whole thing is going down like a belly flop and it hits the water from the near side to the middle (easily a result of connections to the piece that (briefly) didn't fall that held up the middle a bit).

what do I know, I've taken all of 2 structural design classes - and those were more than a decade ago. have to wait for the experts, bet they nail it - especially with the construction going on they should have pretty good notes and probably pictures of problem areas as well as stuff that looked OK to compare to the debris.

I wonder how long before the local news pulls out their stories from a near collapse we had in Albany a couple of years ago - one end of a span dropped causing there to be a rather large speed bump to the next span - something on the order of several feet of a sheer speed bump if I recall correctly.

Ahh, good old FF.G... (Below threshold)
C-C-G Author Profile Page:

Ahh, good old FF.

Get caught in a stupid statement, and then blame the reader.

The classic lefty fast-shuffle.

I was 7 when the Silver Bri... (Below threshold)

I was 7 when the Silver Bridge fell. I remember it very well. My parents had been on the bridge the day before. My Mother was 8 months pregnant with my sister at the time. My Dad also helped with recovery and clean up in the days that followed.

The bridge inspection system was started due to the collapse of the Silver Bridge.

FreedomFries, perhaps you s... (Below threshold)

FreedomFries, perhaps you should consider why no one can tell the difference between your joke and your normal run of comment?

The lefty blogs are all ove... (Below threshold)
Beeblebrox:

The lefty blogs are all over this as a failure of the Bush admin and more specifically, him spending on the war rather than on infrastructure.

This is how truly stupid these people are. Simply amazing.

Accidents can happen sudden... (Below threshold)

Accidents can happen suddenly and unexpectedly any time you drive. Yesterday, I had some sort of sudden wheel bearing failure on the front wheel of my motor scooter and was thrown over the handlebars at 25mph and run over by my bike. Today, I have at least 16 injuries including one leg that isn't very good at all. There was plenty of blood as well, but a motorcyclist and his wife and other neighbors offered me medical help at the accident scene. Part of the brotherhood of bikers.

Many bridges are getting old and were never intended for the amount of traffic on them. But the overwelming odds are still that the average person will face a motor vehicle accident somewhere else but from a falling bridge. At the local level, keeping bridges in good condition is a city and state issue, although federal grants do help.

Repubs r far from running t... (Below threshold)
914:

Repubs r far from running this nanny state.!! STO.. The illegals are not very skilled at bridge construction..evidently..Bush did it!

As far as any relation that... (Below threshold)

As far as any relation that the bridge collapse might have to shortages of funds for "infrastructure", as Glenn Reynolds links to Reason, it seems that Minneapolis thought that a priority infrastructure was spending hundreds of millions of public dollars on a new baseball stadium.

There was a time when all b... (Below threshold)
G B P II:

There was a time when all bridges had redundancy - unfortunately governments (whether run at the time by dems or repubs) started that "lowest bidder" poo. There is a reason that the lowest bidder is the lowest bidder, and a reason why the least expensive design is least expensive. Also, there are several bridges I can think of that have had their capacity increased by turning the breakdown lane into another traffic lane. What does that do to the structural reserve? Was that done with the I-35W bridge? 2 other examples: The Brent Spence Bridge carrying I-71 & I-75 over the Ohio River, and the Daniel Carter Beard Bridge carrying I-471 over the Ohio River.




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