Possible design flaw found in collapsed U.S. bridge

http://news.scotsman.com/latest.cfm?id=1247802007 ^

[traumer]

MINNEAPOLIS (Reuters) - A week after a deadly bridge collapse, U.S. Navy divers cut through tangled debris with underwater torches and saws on Wednesday in the search for victims while investigators identified a possible flaw in the 40-year-old span's design.

The August 1 rush-hour collapse of the Interstate 35W bridge hurled vehicles into the Mississippi River 65 feet (20 meters) below, with many tumbling onto the bridge's crumpled concrete deck.

Reacting to the disaster, officials demanded inspections of potentially suspect bridges across the United States amid renewed calls to shore up the country's aging infrastructure.

Five people were killed in the bridge collapse, a death toll that was confirmed within a day of incident. Eight other probable victims are listed as missing.

The recovery process has been slowed by huge slabs of steel-reinforced concrete and dangerous chunks of debris submerged in the river's swift, turbid waters. In some cases, divers had to use their fingertips to read license plates.

"This is going to be a process of having to, most likely, pull these vehicles out and do a long-term extraction, taking apart the vehicle to recover evidence, (and) any (human) remains," Minneapolis Police Capt. Mike Martin told reporters.

National Transportation Safety Board investigators said they had found a potential design problem with gusset plates, or steel plates that tie together angled steel beams of the bridge's frame.

Investigators are trying to verify loads and stresses on these plates at specific locations as well as the materials used to construct them.

Officials stressed the finding is preliminary and would not say exactly where the plates were located or whether failure would have caused the collapse.

"We are continuing to make progress on this investigation, and each area of inquiry gets us closer to ultimately determining the cause of this tragedy," National Transportation Safety Board Chairman Mark Rosenker said in a statement.

Out of some 100 people injured, only a handful remained in hospitals with one in critical condition.

City officials have called the large number of survivors miraculous.

For the families of the missing it has been an agonizing wait. Members of Minneapolis' large Somali immigrant community are grieving over the presumed death of a 23-year-old nursing student, who was pregnant, and her 2-year-old daughter.

Minnesota officials were quickly laying the groundwork for replacing the vital eight-lane bridge, which had been the state's busiest with 140,000 vehicles crossing it each day.

Construction bids were due on Wednesday and officials hoped to choose a contractor within weeks to build a new bridge by the end of 2008, with the help of $250 million (123 million pounds) promised by the federal government. One proposal called for two spans of five traffic lanes each, with room for light rail or buses.

It was unlikely a new bridge could be completed before the Republican Party convention in September 2008, to be held in neighbouring St. Paul.

[ConservaTexan]

I didn’t know Bush was designing bridges 40 years ago.

[Perdogg]

Maybe Halliburton will get the job.

[traumer]

Was Bush in college at that time ?

[Perdogg]

My guess is, it met code 40 years ago.

[DoughtyOne]

Liar! Heh heh heh... just kidding. I expect that will be the charge on DU.

[calex59]

I didn’t know Bush was designing bridges 40 years ago.

If the sun went nova, in the time it took for the explosion to reach us and wipe out the earth, some liberal would blame Bush for it!

[Doctor Raoul]

Design flaw. We should all write a Letter To The Editor and stick it up the bum of the Bush Derangement Syndrome sufferers.

[DoughtyOne]

What is strance about this is that traffic had been reduced in both directions if reports I heard are true. One would think the load was probably 1/2 what it normally was. Why would it fail now if these plates were the issue?

[hosepipe]

[.. Possible design flaw found in collapsed U.S. bridge ..]

NOW thats funny..

[ButThreeLeftsDo]

Thanks for posting this.

I’ve added the Keyword “35w”.

Please add this to keywords on any threads about this tragedy so everyone can more easily track new developments.

Thanks.....

[umgud]

Of course there’s a design flaw. While we don’t know what initiated the collapse, we do know that because of the design, the whole bridge came down. A proper design wouldn’t have the whole thing coming down when just one section has failed.

[Westbrook]

> I didn’t know Bush was designing bridges 40 years ago.

Doesn’t matter.

It’s STILL his fault for spending all that money in iraq when he could have spent it building new bridges and fixing old ones.
/SARC

Of course, we NEVER hear about the over one TRILLION dollars spent by the US Dept of Education, and how that money could have been better spent building new bridges and fixing old ones.

And since the establishment of the Dept. of Education by President James Earl Carter in 1977, what aspect of American education has improved? Even a teeney, weeney, little bit?

What have we gotten for our TRILLION dollars, besides another bloated government bureaucracy?

[Proud_USA_Republican]

Even though this bridge was designed and built 40 years ago, if Hillary was president, this never would of happened...............

[Hurricane Bruiser]

Many bridges relies upon all sections for support but you are correct that there obviously was a design flaw. Perhaps the workers removed a portion that was in some way supporting the bridge structure.

[metmom]

Good question, but conspiracy theories (about terrorism) will only get you flamed from some quarters.

[Jeff Chandler]

Why would it fail now if these plates were the issue?

One Freeper tied it to the obesity crisis.

[Last Dakotan]

Why would it fail now if these plates were the issue?

A fatigue crack can move through material very slowly, even over a period of years. The final failure through the overloaded remaining material can happen at any load.

I've seen fatigue cracks that leave only 5% of the original material remaining before a rapid final break.

[TXnMA]

The two photos in this post from the live thread at http://www.freerepublic.com/focus/f-news/1874950/posts?page=1659#1659 show what might be construed as a "failed gusset plate".

In the top photo, it is at the right side, on the big horizontal beam. In the bottom photo, it is on the left.

Notice the holes where rivets have pulled out -- and how the plate is buckled.

These photos show the area around the mainspan piers on the south shore where the structure failed laterally, (It toppled to the east) whereas all of the other failed slabs dropped (approximately) straight down.

Many believe this area to be that where the initial failure started...

[Ronzo]

National Transportation Safety Board investigators said they had found a potential design problem with gusset plates, or steel plates that tie together angled steel beams of the bridge's frame.

Investigators are trying to verify loads and stresses on these plates at specific locations as well as the materials used to construct them.

Officials stressed the finding is preliminary and would not say exactly where the plates were located or whether failure would have caused the collapse.

Here is a picture I found on Flickr showing the collapse from ground level...in the left hand side of the frame you can see one of the "gusset plates." Notice how it crumpled just a bit. I don't think this particular plate caused the collapse. Most that I've seen in pictures seemed to have held up just fine...but the ones that failed are probably burried under all that concrete roadway.