what a metal expert said on CNN late last night

[donsu]

he said when metal is aged/stressed it cracks. if one of the beams cracked the bridge might sway and lean one way or the other. but that is not what happened in Minn. all of the beams, straight across, cracked at the same time and it fell straight down. he was mystified as to how that could happen.


did anyone else see this interview?

[The Velveteen Ocelot]

1. How does he know that's what happened?

Sounds like some "expert" is just flapping his gums on the teevee. They don't even have the wreckage out of the water; nobody's done a metallurgical analysis; and the NTSB will probably take up to a year to determine the probable cause.

[porphyrian]

2. Unless he was also an engineering expert, I wouldn't get excited about it.

It's entirely possible that the manner in which the bridge was constructed and/or repaired over the years, as well as the load on top of the bridge (cars) caused it to fail in the manner it did.

[donsu]

5. I came late to the interview so don't know his official title. he was in

a lab with big beams and machines, etc. maybe he taught too?

[porphyrian]

7. I can't say either since I didn't see it. But I don't believe anything the corporate media spews.

Especially when it involves an "expert."

[Buzz Clik]

3. An entire team of experts has been selected to go view the bridge and analyze.

This expert, like Bill Frist during the Terry Schiavo debacle, is at a distinct disadvantage by trying to speculate simply from video tape.

We'll know soon enough. Let's wait for the facts.

[MissWaverly]

9. I am with you, labs are one thing, Minnesota winters another

I think you would have to factor in severe weather, cold, water, wind damage, possible impact of "acid rain"

[Bitwit1234]

4. He didn't listen very well to the news.

This bridge is designed that way. It is hinged so that when it gives way it falls like that. It fell exactly how it was designed to.

[karlrschneider]

6. That's not what happened. One end tilted and fell 50 feet sideways.

...

[donsu]

8. maybe there is a video of the interview someplace. I don't want to

mess up the man's reputation in anyway.

I think he was surprised that the beams all gave way at the same place on the beam and at the same time.

hope there is text or video of the interview.

[FredStembottom]

10. From what I understand........

The ends of such bridges sit on roller bearings to allow for expansion and contraction (which can be pretty substantial here in MN as we go form the upper 90's in summer to well below zero in winter). When something gives way in one place and begins to fall - the ends of the bridge roll right off the bearings.

This type of bridge is also called "fracture critical" which means exactly that it CAN fall all at once from a failure in just one place.

These "fracture critical" designs were abandoned some time ago in favor of designs that don't spread the failure to the whole structure. Probably why modern bridges are so dull and boring to look at! At least compared to the old overhead girder wonders of the past.

*this is just what I have read - I am not an engineer and don't play one on TV.

[sam sarrha]

11. what i heard was the ends were actually on Hinges, when one section fell over it let the rest of the

go and it all fell back.. each span like Damiano's.. inn other words, the ends were both hinges holding the middle up, when a link in the span fell over the tension pulled the rest off one at a time to the other end

[FredStembottom]

12. I have been trying to understand the hinge/roller thing......

In the middle of this graphic is a drawing of the bearings - to me - it looks like hinges on top of rollers. So we apparently are both right.:-)

http://www.startribune.com/10072/rich_media/1341492.html

[sam sarrha]

18. yes i was just elaborating.. when that link broke off and released the tension the span snapped back...

and fell apart... i wasn't disagreeing.. cheap and easy construction and lousy safety design doomed to cause total disaster on the entire bridge not just the single span that failed.

it is a design worthy of charges of negligent homicide

[Mutineer]

19. That's what I understood too

that it did in fact, fall in sections.

[Prisoner_Number_Six]

13. Let's wait until they start hauling off the debris in the dark of night

and destroy it before it can be examined.

THEN we can put on our tin foil hats.

[Cessna Invesco Palin]

14. it was an inside job!

as my poorly edited internet movie will soon make clear

[Junkdrawer]

15. Look...just because the Carlyle Group has entered...

the $Trillion "Privatize the Infrastructure" business...

There's no reason for you to go off the deep end like that....

[donsu]

16. lol

nt

[Ezlivin]

17. We can always trust the authorities

As my snarky post will soon make clear.

[sam sarrha]

20. the Governor vetoed the taxes to fix the bridge 4 times, th last time was MAY 4, Negligent Homicide