Fact vs political fantasy
Yesterday, I talked about Nick Coleman's hyperbolic distortion of the "structurally deficient" classification that the I35W bridge had been hit with. Today, courtesy of Hugh Hewitt, here are some facts about the rating system used in bridge inspections.
First, Minnesota Public Radio gives us an inspection history of bridge 9340 (the I35W River Bridges official designation) including a 2001 Fatigue Evaluation report.
"The research involved installation on both the main trusses and the floor truss to measure the live-load stress ranges. Researchers monitored the strain gages while trucks with known axle weights crossed the bridge under normal traffic.
Researchers then developed two-and three-dimensional finite-element models of the bridge, and used the models to calculate the stress ranges throughout the deck truss.
The bridge's deck truss has not experienced fatigue cracking, but it has many poor fatigue details on the main truss and floor truss system.
The research helped determine that the fatigue cracking of the deck truss is not likely, which means that the bridge should not have any problems with fatigue cracking in the foreseeable future.
As a result, MnDOT does not need to prematurely replace this bridge because of fatigue cracking, avoiding the high costs associated with such a large project. " (emphasis mine)
Then there is this Popular Mechanics look at the tragedy.
"Age and heavy use are by no means isolated conditions. According to a report card released in 2005 by the American Society of Civil Engineers (ASCE), 160,570 bridges, or just over one-quarter of the nation’s 590,750-bridge inventory, were rated structurally deficient or functionally obsolete. The nation’s bridges are being called upon to serve a population that has grown from 200 million to over 300 million since the time the first vehicles rolled across the I-35W bridge. "
Heavy use indeed based on what the Pioneer Press said this morning. (HT Capt Ed)
"The Interstate 35W bridge that collapsed Wednesday was not just "structurally deficient," it was among the 100 worst heavily used bridges in the country. "
The promising news is that the NTSB has multiple videos of the collapse and as such may have an answer as to what caused the collapse sooner rather than later.
"We believe as the bridge began to fall it shifted," he said. "I do not want you to jump to any conclusions that it's all at the southern end. I am not saying that a 50-foot shift created the fall. The rest of the bridge appeared to have collapsed in place."
Rosenker said there are at least three additional videos available of the collapse. He suspected one video could provide a helpful view of the collapse. "
We shall see what the NTSB gets out of these videos. Hopefully once we have answers from them the breathless speculation will finally come to an end.
First, Minnesota Public Radio gives us an inspection history of bridge 9340 (the I35W River Bridges official designation) including a 2001 Fatigue Evaluation report.
"The research involved installation on both the main trusses and the floor truss to measure the live-load stress ranges. Researchers monitored the strain gages while trucks with known axle weights crossed the bridge under normal traffic.
Researchers then developed two-and three-dimensional finite-element models of the bridge, and used the models to calculate the stress ranges throughout the deck truss.
The bridge's deck truss has not experienced fatigue cracking, but it has many poor fatigue details on the main truss and floor truss system.
The research helped determine that the fatigue cracking of the deck truss is not likely, which means that the bridge should not have any problems with fatigue cracking in the foreseeable future.
As a result, MnDOT does not need to prematurely replace this bridge because of fatigue cracking, avoiding the high costs associated with such a large project. " (emphasis mine)
Then there is this Popular Mechanics look at the tragedy.
"Age and heavy use are by no means isolated conditions. According to a report card released in 2005 by the American Society of Civil Engineers (ASCE), 160,570 bridges, or just over one-quarter of the nation’s 590,750-bridge inventory, were rated structurally deficient or functionally obsolete. The nation’s bridges are being called upon to serve a population that has grown from 200 million to over 300 million since the time the first vehicles rolled across the I-35W bridge. "
Heavy use indeed based on what the Pioneer Press said this morning. (HT Capt Ed)
"The Interstate 35W bridge that collapsed Wednesday was not just "structurally deficient," it was among the 100 worst heavily used bridges in the country. "
The promising news is that the NTSB has multiple videos of the collapse and as such may have an answer as to what caused the collapse sooner rather than later.
"We believe as the bridge began to fall it shifted," he said. "I do not want you to jump to any conclusions that it's all at the southern end. I am not saying that a 50-foot shift created the fall. The rest of the bridge appeared to have collapsed in place."
Rosenker said there are at least three additional videos available of the collapse. He suspected one video could provide a helpful view of the collapse. "
We shall see what the NTSB gets out of these videos. Hopefully once we have answers from them the breathless speculation will finally come to an end.
Labels: 35W Bridge collapse
posted by The Lady Logician at
8:05 PM
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