November 2, 2007
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Perhaps this is ”the straw that broke the camels back”. My focus is what caused the undetected weaking of the bridge. From the day after the collapse I cited probably pin/bearings/hinges problems that would not allow the bridge to expand and contract. Like a badly overlaoded vehicle this will take it’s toll over time.
There are simple and cheap measurment tools that can detect if these pins/bearings/hinges are funtioning properly. Basically combine a simple laser ruler with a mirror and couple it to a cellphone. Have it phone in data on the distance of the flex and have a computor compare that to expected paramenters.
To visualise this imagine an open door. You measure the distance between the latch and the base plate. In the case of a bridge this should be a smooth and predictable action. As the girders expand and contract with temperature this distance should change and is thus measurable. This is predictable and a computor can record this and cross check it against expected “flex”.
I could set up a manual demo for under $10. Obviously a more “robust” system and a computor monitoring systems would cost more but it can be done at relatively modest cost. If the unit fails it will not be sending back data within parameters so it will be “flagged”.
http://www.startribune.com/10204/story/1523652.htmlBridge collapse: ‘Working theory’ blames design, weight
U.S. Transportation Secretary Mary Peters said that investigators have a “working theory” of why the I-35W bridge collapsed: a poorly designed gusset plate and excessive weight on the bridge that day.
By Mike Kaszuba and Kevin Diaz, Star Tribune
Last update: November 01, 2007 – 11:42 PM
The top federal transportation official said that investigators have a “working theory” of why the 35W bridge collapsed in August: a poorly designed metal component called a gusset plate and excessive weight on the bridge that day.
U.S. Transportation Secretary Mary Peters’ comments Thursday mirrored statements she made in August, a week after the collapse, and like her previous comments immediately led to controversy. The National Transportation Safety Board, which is investigating the collapse, has said a formal finding will not be available for at least a year.
Sen. Steve Murphy, chairman of the Senate Transportation Committee, said Peters told a gathering Thursday in Washington, D.C., that he attended that “a finding of fault was not going to be lack of inspection or lack of maintenance” by state officials.
“I think it taints the findings,” he said.
But a spokesman for Peters said Murphy’s account of her comments was inaccurate.
“What she said is, look, I’m not going to prejudge what the NTSB is going to find, but the working theory that they are operating on, and this has been in the news for about two months now, is that there was a combination of a gusset plate and too much weight placed on a certain part of the bridge,” spokesman Brian Turmail said.
“Certainly, the NTSB would want to look into whether lack of maintenance was a factor in the collapse of the bridge,” he said. But Turmail added that “the working theory at the NTSB is that it is not a lack of inspections, but a design flaw and weight.”
Later Thursday, Rep. Ron Erhardt, R-Edina, confirmed Murphy’s account. “Murphy was sitting behind me and I turned to him and said, ‘What is this?’” Erhardt said. “To hear that it wasn’t maintenance or inspection, I thought, ‘What the hell?’ I remembered early reports about the gussets and I thought, what is that but lack of maintenance?”
Peters’ remarks came during a formal address to the White House Transportation Legislative Leaders Summit.
A design flaw would give administration critics less of an opening to hold current officials at the Minnesota Department of Transportation or Gov. Tim Pawlenty responsible.
“It’s true, yeah, we are looking at the design issues and the gusset plates and the weight of the construction materials and equipment on the bridge,” NTSB spokesman Peter Knudson said. “We’re also looking at the maintenance and repair history. We’re looking at the de-icing fluids — any role they may have played. We basically haven’t ruled anything out yet.”
Staff writer Patricia Lopez contributed to this report.
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