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#1
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Design flaw cited in MN bridge collapse
FYI...
It makes one wonder how many more of these under sized gusset plates are out there waiting to be found.... TMT Design flaw cited in bridge collapse By FREDERIC J. FROMMER, Associated Press Writer Steel plates connecting beams in the Interstate 35W bridge in Minneapolis were too thin by half and fractured, "the critical factor" in the collapse that killed 13 people and injured 145, the National Transportation Safety Board said Tuesday. The connectors, called gusset plates, were roughly half the 1-inch thickness they should have been because of a design error, NTSB Chairman Mark Rosenker said. Investigators found 16 fractured gusset plates from the bridge's center span. "It is the undersizing of the design which we believe is the critical factor here. It is the critical factor that began the process of this collapse. That's what failed," Rosenker said at a news conference. What caused the bridge to collapse during rush-hour traffic in the early evening of Aug. 1 -- "the straw that broke the camel's back," as Rosenker put it -- was not yet known, he said. A final report by the NTSB was expected this fall. The Minneapolis span was a steel-deck truss bridge that opened in 1967. Rosenker said it wasn't clear how the design flaw made it into the bridge because investigators couldn't find the design calculations. The bridge was called "fracture critical," or lacking redundancies, meaning that a failure of any number of structural elements would cause the entire bridge to collapse. Rosenker said the safety board had no evidence that the deficiencies in the Minneapolis bridge design "are widespread or go beyond this bridge." However, the NTSB couldn't discount the possibility of similar errors in other like bridges, he said, and cautioned that states and contractors should look at the original design calculations for such bridges before they undertake "future operational changes." The NTSB issued a safety recommendation to the Transportation Department's Federal Highway Administration suggesting that the agency require bridge owners to do so. Transportation Secretary Mary Peters called on states to calculate how changes in bridge weight, capacity or evolving bridge conditions will affect gusset plates. "With a few calculations, we can help reassure travelers that our bridges remain safe," Peters said in a statement. Rosenker noted that structural weight had been added to the Minneapolis bridge in two major renovations, in the 1970s and 1990s. "When they added the weight they didn't realize they were bringing the margins of safety down to where they didn't exist anymore," he said. Rosenker said that construction materials on the bridge the day it collapsed, which were part of a resurfacing project, added about 300 tons and were on the same side where failure of the bridge began. Asked if the construction was the tipping point, Rosenker said, "I'm not ruling it in, and I'm not ruling it out." That will be left to the final report to determine, he said. Abolhassan Astaneh-Asl, a professor of civil and environmental engineering at the University of California at Berkeley and an expert on gussets, spent 10 days in Minneapolis after the collapse gathering information for his own research. "I concluded that the construction load may have been the last straw," he said. Last August, Peters advised states to consider the additional stress placed on bridges during construction projects. Rosenker said there was little chance that bridge inspectors would have noticed undersized gusset plates. "No one recognized that you could undersize a gusset plate," Rosenker said. "In the history of this organization, we have not seen anything like this before," he said, adding that gusset plates are supposed to be stronger than the beams they connect. "It was a shock, if you will, to the investigating team." Dan Dorgan, the state bridge engineer in Minnesota, said that the assumption is that gussets wouldn't be the weakest point in the design. "And, in fact, computer programs that generally model these bridges typically do not take gusset plates into consideration," Dorgan said. "They mainly look at the main members." The Minneapolis bridge was deemed "structurally deficient" by the federal government as far back as 1990, and the state's maintenance of the structure has been questioned. But Rosenker said the NTSB investigation has found no evidence that cracking, corrosion or other wear "played any role in the collapse of the bridge." Investigators also found no flaws in the steel and concrete material used in the bridge. The bridge was originally designed by Sverdrup & Parcel, a company acquired in 1999 by Jacobs Engineering Group Inc. of Pasadena, Calif. A message left by The Associated Press with Jacobs Engineering wasn't immediately returned. Minnesota Gov. Tim Pawlenty noted that he had warned others not to jump to conclusions about the collapse. Pawlenty and his transportation commissioner, Lt. Gov. Carol Molnau, have been sharply criticized over state funding for infrastructure and maintenance. "While the NTSB investigation is not complete, the focus of the investigation appears headed in a direction different than many of the political claims that have been made," Pawlenty said. Minnesota is reviewing 23 state bridges with truss designs to make sure their current load ratings fit with the gusset design. Officials hope to complete the state reviews by June at a cost of $500,000. There are another 36 such bridges controlled by municipal governments in Minnesota. Late last year, President Bush signed a massive spending bill that included $195 million to help replace the bridge. That came on top of the $178.5 million the federal government had already given Minnesota for the project. ___ Associated Press reporters Brian Bakst in St. Paul and Steve Karnowski in Minneapolis contributed to this story. |
#2
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Design flaw cited in MN bridge collapse
I don't think I buy it. Follow the money and find where the payola is
squashing the real cause. How old was that bridge? 45-50 something?. More likely scenario: the construction gang on the span at the time of collapse-"Hey Boss-I done pulled thet pin yoo toll me two..." "NOT *THAT* PIN!!!!AAAAGGGHHHHH............." JR Dweller in the cellar Too_Many_Tools wrote: FYI... It makes one wonder how many more of these under sized gusset plates are out there waiting to be found.... TMT Design flaw cited in bridge collapse By FREDERIC J. FROMMER, Associated Press Writer Steel plates connecting beams in the Interstate 35W bridge in Minneapolis were too thin by half and fractured, "the critical factor" in the collapse that killed 13 people and injured 145, the National Transportation Safety Board said Tuesday. The connectors, called gusset plates, were roughly half the 1-inch thickness they should have been because of a design error, NTSB Chairman Mark Rosenker said. Investigators found 16 fractured gusset plates from the bridge's center span. "It is the undersizing of the design which we believe is the critical factor here. It is the critical factor that began the process of this collapse. That's what failed," Rosenker said at a news conference. What caused the bridge to collapse during rush-hour traffic in the early evening of Aug. 1 -- "the straw that broke the camel's back," as Rosenker put it -- was not yet known, he said. A final report by the NTSB was expected this fall. The Minneapolis span was a steel-deck truss bridge that opened in 1967. Rosenker said it wasn't clear how the design flaw made it into the bridge because investigators couldn't find the design calculations. The bridge was called "fracture critical," or lacking redundancies, meaning that a failure of any number of structural elements would cause the entire bridge to collapse. Rosenker said the safety board had no evidence that the deficiencies in the Minneapolis bridge design "are widespread or go beyond this bridge." However, the NTSB couldn't discount the possibility of similar errors in other like bridges, he said, and cautioned that states and contractors should look at the original design calculations for such bridges before they undertake "future operational changes." The NTSB issued a safety recommendation to the Transportation Department's Federal Highway Administration suggesting that the agency require bridge owners to do so. Transportation Secretary Mary Peters called on states to calculate how changes in bridge weight, capacity or evolving bridge conditions will affect gusset plates. "With a few calculations, we can help reassure travelers that our bridges remain safe," Peters said in a statement. Rosenker noted that structural weight had been added to the Minneapolis bridge in two major renovations, in the 1970s and 1990s. "When they added the weight they didn't realize they were bringing the margins of safety down to where they didn't exist anymore," he said. Rosenker said that construction materials on the bridge the day it collapsed, which were part of a resurfacing project, added about 300 tons and were on the same side where failure of the bridge began. Asked if the construction was the tipping point, Rosenker said, "I'm not ruling it in, and I'm not ruling it out." That will be left to the final report to determine, he said. Abolhassan Astaneh-Asl, a professor of civil and environmental engineering at the University of California at Berkeley and an expert on gussets, spent 10 days in Minneapolis after the collapse gathering information for his own research. "I concluded that the construction load may have been the last straw," he said. Last August, Peters advised states to consider the additional stress placed on bridges during construction projects. Rosenker said there was little chance that bridge inspectors would have noticed undersized gusset plates. "No one recognized that you could undersize a gusset plate," Rosenker said. "In the history of this organization, we have not seen anything like this before," he said, adding that gusset plates are supposed to be stronger than the beams they connect. "It was a shock, if you will, to the investigating team." Dan Dorgan, the state bridge engineer in Minnesota, said that the assumption is that gussets wouldn't be the weakest point in the design. "And, in fact, computer programs that generally model these bridges typically do not take gusset plates into consideration," Dorgan said. "They mainly look at the main members." The Minneapolis bridge was deemed "structurally deficient" by the federal government as far back as 1990, and the state's maintenance of the structure has been questioned. But Rosenker said the NTSB investigation has found no evidence that cracking, corrosion or other wear "played any role in the collapse of the bridge." Investigators also found no flaws in the steel and concrete material used in the bridge. The bridge was originally designed by Sverdrup & Parcel, a company acquired in 1999 by Jacobs Engineering Group Inc. of Pasadena, Calif. A message left by The Associated Press with Jacobs Engineering wasn't immediately returned. Minnesota Gov. Tim Pawlenty noted that he had warned others not to jump to conclusions about the collapse. Pawlenty and his transportation commissioner, Lt. Gov. Carol Molnau, have been sharply criticized over state funding for infrastructure and maintenance. "While the NTSB investigation is not complete, the focus of the investigation appears headed in a direction different than many of the political claims that have been made," Pawlenty said. Minnesota is reviewing 23 state bridges with truss designs to make sure their current load ratings fit with the gusset design. Officials hope to complete the state reviews by June at a cost of $500,000. There are another 36 such bridges controlled by municipal governments in Minnesota. Late last year, President Bush signed a massive spending bill that included $195 million to help replace the bridge. That came on top of the $178.5 million the federal government had already given Minnesota for the project. ___ Associated Press reporters Brian Bakst in St. Paul and Steve Karnowski in Minneapolis contributed to this story. -- -------------------------------------------------------------- Home Page: http://www.seanet.com/~jasonrnorth If you're not the lead dog, the view never changes Doubt yourself, and the real world will eat you alive The world doesn't revolve around you, it revolves around me No skeletons in the closet; just decomposing corpses -------------------------------------------------------------- Dependence is Vulnerability: -------------------------------------------------------------- "Open the Pod Bay Doors please, Hal" "I'm sorry, Dave, I'm afraid I can't do that.." |
#3
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Design flaw cited in MN bridge collapse
JR North wrote:
I don't think I buy it. Follow the money and find where the payola is squashing the real cause. How old was that bridge? 45-50 something?. More likely scenario: the construction gang on the span at the time of collapse-"Hey Boss-I done pulled thet pin yoo toll me two..." "NOT *THAT* PIN!!!!AAAAGGGHHHHH............." JR Dweller in the cellar Certainly a possibility. More likely the bridge was engineered correctly at first, and somewhere in the drafting to the final plans the gusset size was misapplied as "half this thickness per side", instead of "this thickness per side" and then the construction crew didn't mention to the engineer that the thickness was half of what they were used to from other bridges. |
#4
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Design flaw cited in MN bridge collapse
On Jan 15, 6:27*pm, "Pete C." wrote:
JR North wrote: I don't think I buy it. Follow the money and find where the payola is squashing the real cause. How old was that bridge? 45-50 something?. More likely scenario: the construction gang on the span at the time of collapse-"Hey Boss-I done pulled thet pin yoo toll me two..." "NOT *THAT* PIN!!!!AAAAGGGHHHHH............." JR Dweller in the cellar Certainly a possibility. More likely the bridge was engineered correctly at first, and somewhere in the drafting to the final plans the gusset size was misapplied as "half this thickness per side", instead of "this thickness per side" and then the construction crew didn't mention to the engineer that the thickness was half of what they were used to from other bridges. Yeah..I am a bit surprised on this explanation. Gussets are something that one does check. TMT |
#5
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Design flaw cited in MN bridge collapse
On Tue, 15 Jan 2008 16:43:37 -0800 (PST), Too_Many_Tools
wrote: On Jan 15, 6:27*pm, "Pete C." wrote: JR North wrote: I don't think I buy it. Follow the money and find where the payola is squashing the real cause. How old was that bridge? 45-50 something?. More likely scenario: the construction gang on the span at the time of collapse-"Hey Boss-I done pulled thet pin yoo toll me two..." "NOT *THAT* PIN!!!!AAAAGGGHHHHH............." JR Dweller in the cellar Certainly a possibility. More likely the bridge was engineered correctly at first, and somewhere in the drafting to the final plans the gusset size was misapplied as "half this thickness per side", instead of "this thickness per side" and then the construction crew didn't mention to the engineer that the thickness was half of what they were used to from other bridges. Yeah..I am a bit surprised on this explanation. Gussets are something that one does check. TMT May be, but if the findings are negative they get suppressed by the pols. Case of that in today's Mnpls paper re the Hastings bridge. Inspectors found some serious problems but the MNDOT commissioner (and Lt. Guv) suppressed the reports. Several times. It seems that the Dems in the legislature are reluctant to give her the boot because she is such a visible political liablity for the GOP Guv who is now scurrying like hell to distance himself from her although she was his pick for the job(s). Freakin' politicians! |
#6
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Design flaw cited in MN bridge collapse
On Jan 16, 1:27 am, Don Foreman wrote:
On Tue, 15 Jan 2008 16:43:37 -0800 (PST), Too_Many_Tools wrote: On Jan 15, 6:27 pm, "Pete C." wrote: JR North wrote: I don't think I buy it. Follow the money and find where the payola is squashing the real cause. How old was that bridge? 45-50 something?. More likely scenario: the construction gang on the span at the time of collapse-"Hey Boss-I done pulled thet pin yoo toll me two..." "NOT *THAT* PIN!!!!AAAAGGGHHHHH............." JR Dweller in the cellar Certainly a possibility. More likely the bridge was engineered correctly at first, and somewhere in the drafting to the final plans the gusset size was misapplied as "half this thickness per side", instead of "this thickness per side" and then the construction crew didn't mention to the engineer that the thickness was half of what they were used to from other bridges. Yeah..I am a bit surprised on this explanation. Gussets are something that one does check. TMT May be, but if the findings are negative they get suppressed by the pols. Case of that in today's Mnpls paper re the Hastings bridge. Inspectors found some serious problems but the MNDOT commissioner (and Lt. Guv) suppressed the reports. Several times. It seems that the Dems in the legislature are reluctant to give her the boot because she is such a visible political liablity for the GOP Guv who is now scurrying like hell to distance himself from her although she was his pick for the job(s). Freakin' politicians! You guys had a good politician, Governor Jessie Ventura, HONEST, but could not stop from telling the truth to the point of political incorrectness. "Religion is for those with weak minds". Which I agree with, but you don't tell that to your constituents in a Playboy interview. Of course you could get yourself another HHH super liberal. His legacy lives on. ignator |
#7
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Design flaw cited in MN bridge collapse
On Jan 16, 1:27*am, Don Foreman wrote:
On Tue, 15 Jan 2008 16:43:37 -0800 (PST), Too_Many_Tools wrote: On Jan 15, 6:27*pm, "Pete C." wrote: JR North wrote: I don't think I buy it. Follow the money and find where the payola is squashing the real cause. How old was that bridge? 45-50 something?. More likely scenario: the construction gang on the span at the time of collapse-"Hey Boss-I done pulled thet pin yoo toll me two..." "NOT *THAT* PIN!!!!AAAAGGGHHHHH............." JR Dweller in the cellar Certainly a possibility. More likely the bridge was engineered correctly at first, and somewhere in the drafting to the final plans the gusset size was misapplied as "half this thickness per side", instead of "this thickness per side" and then the construction crew didn't mention to the engineer that the thickness was half of what they were used to from other bridges. Yeah..I am a bit surprised on this explanation. Gussets are something that one does check. TMT May be, but if the findings are negative they get suppressed by the pols. *Case of that in today's Mnpls paper re the Hastings bridge. Inspectors found some serious problems but *the MNDOT commissioner (and Lt. Guv) *suppressed the reports. Several times. * It seems that the *Dems in the legislature *are reluctant to give her the boot because she is such a visible *political liablity for the GOP Guv who is now scurrying like hell to distance himself from her although she was his pick for the job(s). * Freakin' politicians! *- Hide quoted text - - Show quoted text - Kinda like the Democrats in Washington keeping George and Dick around.... George is working very hard to get a Democrat in the White House. TMT |
#8
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Design flaw cited in MN bridge collapse
"Pete C." wrote in message ... JR North wrote: I don't think I buy it. Follow the money and find where the payola is squashing the real cause. How old was that bridge? 45-50 something?. More likely scenario: the construction gang on the span at the time of collapse-"Hey Boss-I done pulled thet pin yoo toll me two..." "NOT *THAT* PIN!!!!AAAAGGGHHHHH............." JR Dweller in the cellar Certainly a possibility. More likely the bridge was engineered correctly at first, and somewhere in the drafting to the final plans the gusset size was misapplied as "half this thickness per side", instead of "this thickness per side" and then the construction crew didn't mention to the engineer that the thickness was half of what they were used to from other bridges. More likely, the construction crew mentioned it to the manager, he told his manager, who ignored it. In my experience, the guys on the front lines of any business spot a potentially huge problem and report it, the message never reaches anyone who can do anything about it. I've worked in a variety of industries and from what I've seen, this is pretty much universal. I have no idea why. |
#9
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Design flaw cited in MN bridge collapse
Adam Corolla wrote:
More likely, the construction crew mentioned it to the manager, he told his manager, who ignored it. In my experience, the guys on the front lines of any business spot a potentially huge problem and report it, the message never reaches anyone who can do anything about it. I've worked in a variety of industries and from what I've seen, this is pretty much universal. I have no idea why. Dunno if it applies in those worlds, but around my world, it would be called the "sunshine filter". Guys think they won't ever get the next pay raise or promotion if they deliver bad news or problems, so they filter them out, and will only blow purified sunshine up the boss's arse. Spinless gits, as often as not. The ones with spines deal with the problems, or if they cannot, pass them on to those that can. Cheers Trevor Jones |
#10
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Design flaw cited in MN bridge collapse
On Jan 16, 5:14*pm, Trevor Jones wrote:
Adam Corolla wrote: More likely, the construction crew mentioned it to the manager, he told his manager, who ignored it. *In my experience, the guys on the front lines of any business spot a potentially huge problem and report it, the message never reaches anyone who can do anything about it. *I've worked in a variety of industries and from what I've seen, this is pretty much universal. *I have no idea why. * Dunno if it applies in those worlds, but around my world, it would be called the "sunshine filter". * Guys think they won't ever get the next pay raise or promotion if they deliver bad news or problems, so they filter them out, and will only blow purified sunshine up the boss's arse. * Spinless gits, as often as not. The ones with spines deal with the problems, or if they cannot, pass them on to those that can. * Cheers * *Trevor Jones "Sunshine filtering" is an universal truth. The messenger is always killed. TMT |
#11
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Design flaw cited in MN bridge collapse
"Trevor Jones" wrote in message news:edwjj.6978$yQ1.3473@edtnps89... Adam Corolla wrote: More likely, the construction crew mentioned it to the manager, he told his manager, who ignored it. In my experience, the guys on the front lines of any business spot a potentially huge problem and report it, the message never reaches anyone who can do anything about it. I've worked in a variety of industries and from what I've seen, this is pretty much universal. I have no idea why. Dunno if it applies in those worlds, but around my world, it would be called the "sunshine filter". Guys think they won't ever get the next pay raise or promotion if they deliver bad news or problems, so they filter them out, and will only blow purified sunshine up the boss's arse. Spinless gits, as often as not. The ones with spines deal with the problems, or if they cannot, pass them on to those that can. Cheers Trevor Jones I believe you have nailed it. Most of the managers I've known, while many were nice enough guys and had at least adequate smarts, would cower in fear at the mere mention of rocking the boat. |
#12
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Design flaw cited in MN bridge collapse
On Jan 16, 2:29*pm, "Adam Corolla"
wrote: "Pete C." wrote in message ... JR North wrote: I don't think I buy it. Follow the money and find where the payola is squashing the real cause. How old was that bridge? 45-50 something?. More likely scenario: the construction gang on the span at the time of collapse-"Hey Boss-I done pulled thet pin yoo toll me two..." "NOT *THAT* PIN!!!!AAAAGGGHHHHH............." JR Dweller in the cellar Certainly a possibility. More likely the bridge was engineered correctly at first, and somewhere in the drafting to the final plans the gusset size was misapplied as "half this thickness per side", instead of "this thickness per side" and then the construction crew didn't mention to the engineer that the thickness was half of what they were used to from other bridges. More likely, the construction crew mentioned it to the manager, he told his manager, who ignored it. *In my experience, the guys on the front lines of any business spot a potentially huge problem and report it, the message never reaches anyone who can do anything about it. *I've worked in a variety of industries and from what I've seen, this is pretty much universal. *I have no idea why.- Hide quoted text - - Show quoted text - I would agre that this happens ALOT. But in the end the structure is supposed to be inspected. If the report is true (and we have yet to see the final version), then that process broke down. It would not surprise me to learn that the bridge was carrying more than it was designed for...without authorization. TMT |
#13
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Design flaw cited in MN bridge collapse
On Wed, 16 Jan 2008 20:16:33 -0800 (PST), Too_Many_Tools
wrote: On Jan 16, 2:29*pm, "Adam Corolla" wrote: "Pete C." wrote in message ... I would agre that this happens ALOT. But in the end the structure is supposed to be inspected. When I started in Project Management in 1964, I stayed on a major project from tender award to final acceptance. By the time I retired in 1994, I was lucky to make a site visit more than once per week. In the early years, the contractor was free to ask my advise or suggest alternatives, after my move to regional office, management attitude was "let him build it as it was designed, and, let him figure it out for himself. If he does it wrong, make him do it over (if we catch it)" and ALL CONRACTORS ARE CROOKS. Need I say I was happy to take the retirement package when it was offered. If the report is true (and we have yet to see the final version), then that process broke down. It would not surprise me to learn that the bridge was carrying more than it was designed for...without authorization. TMT Gerry :-)} London, Canada |
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