|
NTSB details investigation progress
NTSB Chairman Mark Rosenker said the investigation into the reason why the Interstate 35W Bridge collapsed is moving along and all of the necessary computer equipment will be in place by this weekend. Rosenker said the investigators spent Friday focusing on the southern part of the bridge. The reason is, "We noticed that the section of this part of the bridge behaved differently in the video and in the way it sat in the final collapse." He said that the top section of the bridge shifted 50 feet to the east and the structural part fell a bit west. The rest of the bridge collapsed in place. "We believe that as the bridge began to fall it shifted and that's all I am saying," said Rosenker, adding "When you compare it to the rest of the bridge which appeared to collapse in place." What we have is a step forward he said. He refused to elaborate saying to do so would be to begin analyzing the cause, something Rosenker said he would not do. He said looking at the debris and structure of southern end, a failure at the northern end could transfer loads to the southern end and trigger the collapse. "So, we don't have an answer, we have a starting point," said Rosenker. He repeatedly said he won't speculate on any reason for this collapse. "We are not going to take a short cut." He said that investigators were going to take a look at any unique design features that could have created a shift of 50 feet. To assist investigators they'll be using an advanced computer program called Finite Element Analysis. This program allows the investigators to take elements of the bridge off and watch it collapse in the computer program. Rosenker said a host of failure scenarios will be examined and the computer technicians will give the information to the NTSB. That analysis is supposed to begin on Monday. Rosenker and his team will also be using a 3D mapping device that will scan 360 degrees of the debris field and map it. That way, said Rosenker, when investigators get back to Washington D.C. they'll have a complete 3D computer image of the debris field. He also reported that the Army Corps of Engineers has three other videos of the collapse area in addition to the one that's already been released to the media. Rosenker said the FBI has the one tape that provides collapse from another view and he said they were working to enhance that tape. The other two may not help much as they were from wrong direction. Reassembling the bridge: On Thursday, Chairman Rosenker said the entire bridge would be reconstructed on its side at a location down river from the collapse. But Friday, he backed off of that plan and said only pieces would need to be reassembled. "We may cut out sections or take pieces that we are interested in and take those parts and analyze them in Washington." They'll be moving the bridge parts that they do wish to reassemble down river to a staging area. But, cautioned Rosenker, the parts will only be removed after the entire debris field has been mapped and computerized. He said his team was looking at the bridge inspection reports line by line and if they find that even though state inspectors followed the regulations this still happened, then they'll examine the regulations. If they don't seem up to snuff then they'll recommend changes be made nationwide. Rosenker again cautioned that it will take months to find out why a main link between north and south metro collapsed into the river, killing at least five and injuring dozens more. (Copyright 2007 by KARE. All Rights Reserved.)
|
 People who can give eyewitness descriptions of the bridge's collapse have been asked to call a toll-free line established by the National Transportation Safety Board. The board also wants to hear from those caught up in the collapse and those with photos of the collapse or its immediate aftermath. The number is 1-866-328-6347.
MORE HEADLINES |
||||||||||||||||||||||||||
|
