Poor design led to I-35W bridge collapse?

This image shows the ground supports of the bridge before the collapse:
http://www.wmur.com/2007/0802/13805989_240X180.jpg
taken from:
Nation's Bridges Face Immediate Inspection. Fifth Victim Found; President Bush To Visit Minneapolis UPDATED: 9:20 am EDT August 3, 2007 http://www.wmur.com/news/13801620/detail.html
A video of the collapse is also available on this page.
Note the ground supports are slender concrete columns. Note also the steel arch only extends to the top of the support. It does not extend down into the ground. In contrast note the arches of the 10th Avenue bridge next to the collapsed bridge extend into the ground:
10th Avenue Bridge. http://en.wikipedia.org/wiki/10th_Avenue_Bridge
The strength of an arch extends from its curvature. Note that an arch of the I-35W bridge not extending into the ground means the arch is shorter which necessarily makes the arch straighter, and therefore weaker. The 10th Avenue Bridge also has supports in the middle of the river while the I-35W bridge did not. Compared to the supports of the 10th Avenue Bridge, the ground supports of the I-35W bridge can only be described as flimsy. This is a bridge that carries the most traffic in the state of Minnesota. Moreover the 10th Avenue bridge only has to carry 2 lanes, while the I-35W carried 8. A professor at Northwestern argues the failure was likely due to the joints connecting the bridge to the concrete supports:
Investigators in bridge collapse focus on chilling video. By Jon Hilkevitch | Tribune transportation reporter 9:41 PM CDT, August 2, 2007 "The bridge must have been near a state of collapse for some time, and the construction might have contributed to its failure," said Zdenek Bazant, a professor of civil and environmental engineering at Northwestern University. Bazant said he suspects there may have been a hairline crack or fatigue in the steel joints near bridge supports, leading to the buckling" http://www.chicagotribune.com/services/newspaper/premium/printedition/Friday/chi-070802bridge,0,3911616.story?page=2
This page on the I-35W describes it as a truss bridge:
I-35W Mississippi River bridge. http://en.wikipedia.org/wiki/I-35W_Mississippi_River_bridge
These are among the cheapest and flimsiest of bridges. They lack the redundancy of many other types of bridges:
Investigators in bridge collapse focus on chilling video. By Jon Hilkevitch | Tribune transportation reporter 9:41 PM CDT, August 2, 2007 "Other engineering experts said that the 1960s-design of steel-arched bridges did not contain structural redundancies, meaning that if one component fails, the whole structure is in jeopardy because the weight does not shift to other points on the bridge. "We know that we would not build a bridge like this today,'' said Kent Harries, an assistant engineering professor at the University of Pittsburgh." http://www.chicagotribune.com/services/newspaper/premium/printedition/Friday/chi-070802bridge,0,3911616.story?page=2
Bob Clark
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Dear Robert Clark:

The bridge was inspected and noted to have accumulated flaws: 1) corrosion in / near bearing surfaces (a maintenance item), and 2) fatigue cracks (indicating loading or aging in excess of design).
Maintenance on *these things* were not underway. They decided to inspect it more often, to see if maybe inspection would fix them. They can afford inspectors, but they cannot / would not afford the repairs.
And there are 17,000 more bridges with similar diagnoses.
The purpose of government is to do for the people what they cannot do for themselves. "Lack of planning" they can do for themselves. It takes government to "cut taxes at the expense of basic services".
Robert, I don't think it was the engineering. I'd bet the engineer that designed the bridge did not design it for an infinite, (effectively) unmaintained lifetime. And I'd also guess that there are more lanes of traffic painted across that stretch of concrete than the engineer was told to design for so many years ago.
I'd say (from my armchair) the root cause was routinely exceeding the design loading and not performing necessary maintenance.
David A. Smith
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http://www.chicagotribune.com/services/newspaper/premium/printedition/Friday/chi-070802bridge,0,3911616.story?page=2
http://www.chicagotribune.com/services/newspaper/premium/printedition/Friday/chi-070802bridge,0,3911616.story?page=2
"The purpose of government is to do for the people what they cannot do for themselves. "Lack of planning" they can do for themselves. It takes government to "cut taxes at the expense of basic services".
This is not true, I have yet to see the government bring me a beer while I am watching the Science Channel. The purpose of the government is to provide the fundamentals and infrastructure for the general walfare of society. There are some highways and bridges built entirely from private funds and users are charged a fee to driven on them. But generally, roads and bridges are the domain of government. The MN State government obviously failed to provide adequate maintenance for their bridges, electing to provide "More of something else" to their electorate, to "buy" a few more votes for specific politicians, at the expense of the infrastructure.
"I'd say (from my armchair) the root cause was routinely exceeding the design loading and not performing necessary maintenance."
I absolutely agree with this conclusion, but it will take a few months investigation to determine exactly what failed, initially, but when the big pircure is modeled, the above will most likely sum it up.
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Pittsburgh."http://www.chicagotribune.com/services/newspaper/premium/printedition ...
I am in agreement. The flimsy support is quite vulnerable to mechanical damage and corrosion. The consequence of damage/loss of this support is a design disaster... down-grading the entire bridge from a locally fixed shallow arch to a stiffened plate with edge- truss stiffeners, a massive loss of bend/twist rigidity of the arch. It is like removing the keystone not exactly at the center, but like removing some stones at quarter points.An arch of increasing reinforcement cross-sections designed all the way to the base/ground was needed and that should not have been compromised when once began at the mid-span.It would have responded better to unanticipated off- design loads like corrosion weaknesses or flutter of a ribbon bridge assisted by dysfunctional joints.
The tell-tale picture shows fracture roughly at the zones of sudden loss of bend/twist stiffness across span.
Narasimham
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Dear Narasimham:
...

Was it not designed for the design loads "40 years" ago, with the expectation of reasonable maintenance?

The expected mode of failure was triggered by "fatigue" and "corrosion". Both of which require maintenance.
In 2005, had they responded by reducing the number of lanes across this bridge, until funds could be had to do actual repairs, we would or would not be having this discussion?

Your area of expertise is... ?
David A. Smith
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I'm interested in reading what your area of expertise is.
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Dear Irving Layton:

Licensed professional mechanical engineer in the State of Arridzona. Got my degree in machine design (graduated with honors from Arizona State University).
And I have seen "politicians" find more room on the top of bridges for more than 50 years. And "inspect until the problem goes away" for almost as many years.
Are you satisfied, or do you care to snipe some more? The person I was responding to seemed to have some failure analysis capability. I enjoy talking to someone who knows what they are talking about.
David A. Smith
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wrote:

Someone simply asking "I'm interested in reading what your area of expertise is" should not be considered a sniper. That is a very legitimate question.
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...

...
An article in todays Minneapolis Star/Tribune newspaper has some disconcerting information about previous inspection reports.
http://www.startribune.com/10204/story/1350090.html
State bridge inspectors warned for nearly a decade before its collapse that the Interstate 35W bridge had "severe" and "extensive" corrosion of its beams and trusses, "widespread cracking" in spans and missing or broken bolts.
Not only was the superstructure in poor condition, but certain components were "beyond tolerable limits," and one of the bridge's piers had "tilted to the north," they reported.
By 2000, the inspectors wrote that "eventual replacement of the entire structure would be preferable" to redecking the bridge. They added: "If bridge replacement is significantly delayed, the bridge should be re-decked."
That recommendation was repeated in every report afterward, but it never happened.
Since the collapse, public attention has focused on consultant reports in 2006 and 2007 that expressed serious reservations about the bridge. But a Star Tribune review of older reports by state inspectors shows that their concerns had been growing since the mid-'90s. ... However, in every report since 2000, inspectors urged the state to replace bolts in a specific area of the bridge, a job listed each year under "Immediate Maintenance Recommendations." .... "The fatigue cracks in the approach spans that occurred in the late 1990s were addressed by repairs and retrofitting of connections," MnDOT spokesman Kevin Gutknecht said in a written statement. He added that early replacement of the bridge was not considered in part because "no fatigue cracks had occurred in the main truss spans." ... In 1996, reports took on an urgent tone In many cases the reports simply lay out a long list of problems found rather than rating their severity, but in 1996 the inspectors began to take an urgent tone. Noting that a pier supporting steel spans had tilted to the north, the inspectors warned then, "As this will not be repaired in the near future, this area should be closely inspected!"
In 1998, inspectors wrote that "numerous fatigue cracks were found" in the approach spans on the north and south sides of the bridge, which was then three decades old. The report said the cracks were drilled out and the fractured beams reinforced with bolted plates. ... The 1999 report said those cracks were among "areas of major concern," adding that "due to the widespread cracking these areas will now be inspected on six-month intervals."
Later reports recommended only annual inspections. Gutknecht said no further cracking was reported after November 2000, so the monitoring cycle was increased. ... The university's research concluded in 2001 that "fatigue cracking of the deck truss is not likely",...."As a result, MnDOT does not need to prematurely replace this bridge because of fatigue cracking, avoiding the high cost associated with such a large project." ... But MnDOT inspectors continued to express concern about fatigue cracking after the university report and the department asked the engineering design consultant URS to review the bridge's condition.
URS in 2006 expressed concerns that a serious fatigue crack might go undetected because of the difficulty in inspecting parts of the bridge that were difficult to reach. URS recommended steel plating as a fix.
But MnDOT engineers asked URS to come up with other options and the department ultimately chose an alternative that called for increased inspections and repairing any problems found. URS called that option the "most cost efficient," but warned that "the critical issue of this approach is to ensure" that inspectors don't miss any measurable flaws.
Chief bridge engineer Dan Dorgan said previously that MnDOT chose the inspection option because it worried that drilling to add plates might weaken the bridge.
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Structural / Mechanical design engineering for Space launched Composite Structures,about 30 years.
Regards, Narasimham
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Dear Narasimham:
...

Space Shuttle, weapons, or "domestic" structures? Anything that does reuse, multiple cycles (like the external tank of the SS was supposed to)?
I was flabbergasted by this: http://otrc.tamu.edu/Pages/currentwheat.html ... never really thought about carbon composites "corroding".
David A. Smith
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--
> I was flabbergasted by this:http://otrc.tamu.edu/Pages/currentwheat.html
> ... never really thought about carbon composites "corroding".
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Pittsburgh."http://www.chicagotribune.com/services/newspaper/premium/printedition ...
--------------------- i dont ahve much information about thespecific case yet we know generally that steel bridges has a severe problem of corrosion OTHOH concrete bridges ar emuch better from tha tpoint of vew ie much less maintanance problems that is th emain reason that in our counrty we refrain as much as possible from steel bridges of corrosable steel (there are kinds of much less corrosion valnearble steels
th e'fatigue of steel is as well a factor yet we ahve to remember that that bridge was holding on i think more than 40 years !! moreoever the sayndards of desighn take in acount fatigue of material and itis taken in acount in a bigger safely factor (salmmer stresses ) so my guess would be tha tit was more a problem of bad maintanance!!
yet of course i cant judge from tousands of miles away wihtout al lthe needed data and facts anyway if it ia systemtic problem it is obvious that there is an urgaent need to avoid further disasters .. just immagine what could happen if that bridge was not falling to water but on a running train..... ATB Y.Porat ----------------
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On Sun, 05 Aug 2007 02:12:48 -0700

Concrete is not stone, you have problem with carbonation and resistance against a lot of chemicals. A concrete bridge will not last for ever unless you replace some of the concrete now an then.

Fatigue problems are design problems. If you don't call it maintenance to replace details that have shown to have a shorter lifespan than that of the rest of bridge.
40 years is not good for something supposed to last at least 100 years.
But things like this have happened before, and probably will in the future also. http://www.bernd-nebel.de/bruecken/4_desaster/birs/birs.html Out of that accident came Tetmajers formula for inelastic buckling of slender columns.
-- Mvh Anders Lagers
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-------------- i forgot to tell you aht i am a bridge engineer with more than 40 years experiance...
concrete is saied to last more than 15 years
youare right that in some cases it has problems mainly if not properly desighned
ie not enough cover of reinforvement stell or in sea while it demads special concret that is chlorine resistance and there are such . another problem is salt that is spread fo rdifrosting ice
if can be as wel ahndles by soecial coating of the comcrete . yes the satndard of bridges deoand 100 - 150 years of use yeti guess in parctice i tcan last much longer.
--
-----
>
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Dear Anders Lagers:
These charaters in your name are going to be butchered upon posting. My apologies in advance.
wrote:

Absolutely true. There are only two materials (as far as I know) that have an infinite fatigue life: iron loaded to less than 80% of hot rolled steel yield strength, and carbon epoxy composites (I don't recall the load limit, 40% of yield perhaps). Concrete will fail eventually.

That is long for a food or software designer. But that is usually less-than-minimum life for a "permanent" bridge.

A fatigue problem *may* be a design problem. Catastrophic failure due to failure of a "single joint" is a design problem. Any structure that does not very conservatively load steel, and have no other materials in its construction, will have fatigue. And hence requires periodic maintenance, not just periodic inspection.

Like the politicians-in-training that schedule, and actual politicians that fund, maintenance? It would not take much to cut the number of lanes that can be used during any hours, once a finding of "structurally deficient" has been made.

Do you have the design specifications for this particular bridge? * Was this a permanent routing for I-35W, * was this a temporary bridge that simply had its term-of-service extended, * was it designed for the traffic that it was getting 40 years after being put in service, * is it a design standard in Minnesota to make all bridges good for 100 years without maintenance?
Politicians also fund least-cost design, and send work to those that meet their cost limits. Which would be shame on the engineering firm also, should that be the case here.

http://www.bernd-nebel.de/bruecken/4_desaster/birs/birs.html
Or this one, due to contractor shortcuts: http://www.enm.bris.ac.uk/anm/tacoma/tacoma.html ... the engineer found that the contractor had used solid I-beams, rather than I-beams with holes cut in the web to reduce stiffness. He showed that to any that would listen, then committed suicide.
Really, they could have cast iron in a monolithic structure down to bedrock. Why not argue that it is a design flaw that they did not do this?
Civil engineering design, just like anything else, has cost limitations. And it is standard practice to *perform* maintenance on bridges... every municipality on the East Coast of the US with a bridge has a pretty significant annual maintenance budget.
David A. Smith
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On Sun, 5 Aug 2007 09:14:24 -0700, "N:dlzc D:aol T:com \(dlzc\)"

...
Which reminds me: the first iron bridge there ever was, closed to traffic years ago. This bridge at Ironbridge, Bridgenorth developed multiple cracks in the cast ironwork, when traffic multiplied in weight and volume far beyond the Coalbrookdale ironmaster's expectations. Imagine that: After only two hundred years!
Brian Whatcott Altus OK
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wrote: : : : >Do you have the design specifications for this particular bridge? : : >* was it designed for the traffic that it was getting 40 years : >after being put in service? : ... : >David A. Smith : : : Which reminds me: the first iron bridge there ever was, closed to : traffic years ago. This bridge at Ironbridge, Bridgenorth developed : multiple cracks in the cast ironwork, when traffic multiplied in : weight and volume far beyond the Coalbrookdale ironmaster's : expectations. Imagine that: After only two hundred years! : : Brian Whatcott Altus OK
You could have thrown in a picture :-)
http://www.wku.edu/Geo/studyabroad/Britain04/ironbridge.jpg
http://www.virtual-shropshire.co.uk/commenu/ironbridge.jpg
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Notably, the bridge has a high, curved arch, which extends all the way to the ground.
Bob Clark
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wrote: : > : > : : > : : > : >Do you have the design specifications for this particular bridge? : > : : > : >* was it designed for the traffic that it was getting 40 years : > : >after being put in service? : > : ... : > : >David A. Smith : > : : > : : > : Which reminds me: the first iron bridge there ever was, closed to : > : traffic years ago. This bridge at Ironbridge, Bridgenorth developed : > : multiple cracks in the cast ironwork, when traffic multiplied in : > : weight and volume far beyond the Coalbrookdale ironmaster's : > : expectations. Imagine that: After only two hundred years! : > : : > : Brian Whatcott Altus OK : > : > You could have thrown in a picture :-) : >
http://www.wku.edu/Geo/studyabroad/Britain04/ironbridge.jpg
: >
http://www.virtual-shropshire.co.uk/commenu/ironbridge.jpg
: : Notably, the bridge has a high, curved arch, which extends all the : way to the ground. : : : Bob Clark
Imagine that... all the way down to the ground, huh? Amazing. I had a girlfriend with legs so long they went all the way up to her arse.
So that's where McDonald's got the idea for their sign from...
http://www.visitingdc.com/images/st-louis-arch-address.jpg
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