A Metallurgist's Insights Into the Minneapolis Bridge Disaster

By Joel S. Hirschhorn
Published August 02, 2007

The incredible collapse of the Minneapolis bridge will send a message to the US that has been repeatedly sent for decades, but to which the political system has refused to effectively respond. America's physical, engineered infrastructure has been in desperate need for massive spending to repair and replace, but the multi-trillion-dollar cost has been rejected by local, state and federal politicians.

First, understand that I have a professional background in this area. My career started as a metallurgist, then I obtained a Ph.D. in Materials Engineering and became a full professor of metallurgical engineering at the University of Wisconsin, Madison, where I taught about mechanical metallurgy and failure analysis, and in my consulting practice regularly worked on explaining actual failures of products and systems.

Academic and professional groups have for many years produced countless reports on mounting unpaid public costs for updating our crucial physical infrastructure, including bridges, but going way beyond those to, for example, roads, water and sewer systems, tunnels and much more.

Make no mistake: The deeply researched and totally supported case for a massive national infrastructure spending program could not have been clearer. But spending on infrastructure is not sexy and politicians at ALL levels of government have found countless excuses for not facing the totality of the problem.

Instead, public spending is dribbled out, dealing with the most urgent problems or, worse yet, the ones that are the most visible to the public. Left unaddressed are massive numbers of problems, such as the Minneapolis bridge and thousands more bridges, that our bureaucratic system has learned to game, postpone, rationalize and, therefore, put the public safety at considerable risk.

I can pretty much assure you that if there is a technically honest and complete investigation, the ultimate explanation of the Minneapolis bridge failure will be related to fatigue cracking in the metal structure.

Already, news reports have revealed some prior observation of a fatigue problem with the bridge and that the bridge had a relatively low rating of four out of a possible nine, showing that it was structurally deficient.

The game played by virtually all government agencies is to find excuses for delaying the most costly repair or replacement of bridges and other parts of the physical infrastructure.

As another example, in most older urban areas there are constant repairs of busted underground water pipes. What is really needed, but avoided, is a total replacement of very old underground pipe systems – in many places 100 or more years old!

Government inspection programs have been terribly compromised over many years. The incredible political pressures to minimize spending on infrastructure have filtered down to the people, procedures and technologies used to examine bridges and other things.

When it comes to bridges it is also important to admit that many aspects of our automobile addiction have raised risks, including enormously greater numbers of vehicles creating heavy traffic during much of the day in urban regions.

Add to this the massive increase in vehicle weight resulting from the incredible increase in monster SUVs, as well as huge increases in large truck traffic.

The Minneapolis bridge collapse happened during evening rush hour because that was a period of maximum stress, and that would be the trigger for expanding existing fatigue cracks.

Once fatigue cracks get to critical sizes they grow and propagate very rapidly, producing powerful loads and stresses on remaining steel components and creating what appears to be a virtually instantaneous bridge collapse.

The remaining public policy question is clear: Will the nation spend what is necessary? Seven other major bridge collapses in the last 40 years have not done the trick. Inadequate bridge inspection has been a frequent documented problem, as well as some design defects.

Many people have already died from bridge failures. But still the nation's elected officials have not bitten the bullet and agreed to spend trillions of dollars over several decades to bring America's physical infrastructure up to the most modern standards.

Think about all this the next time you go over a bridge.

Joel S. Hirschhorn, Ph.D., is the author of Sprawl Kills - How Blandburbs Steal Your Time, Health, and Money. He can be reached through his website: Check out Joel's new book at


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By In MN (anonymous) | Posted August 02, 2007 at 16:20:06

Early reports are the fatigue crack were found a year ago, and allegedly repaired. A local news report asserted that bridge inspectors do not need to have a relevant engineering background. I've worked in a professional technical capacity for the state of MN, and this comes as no surprise to me. Professional employees of the state of MN are amongst the least supported, and when they do find problems, are as often reprimanded for raising issues as they are heeded.

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By jarober (anonymous) | Posted August 02, 2007 at 18:29:45

The "trillion dollar national fix" won't happen. Here's a better idea: hand responsibility for roads over to local governments. They can eiter collect tolls or pass bond issues to pay for upkeep (or raise local taxes, whatever). The point is, the local government will actually be motivated to keep the roads fixed - the local voters will actually vote on catastrophes.

Who is responsible for that now? Everyone (which actually mean no one). Who can be targeted (in an electoral sense) over this failure? No one.

The problem is that the entire funding system is centralized. de-centralize it, and you'll see actual people who have to actually care.

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By Money Politician (anonymous) | Posted August 02, 2007 at 22:18:37

But if you decentralize funding, any cash-strapped locale will not maintain the road/bridge, no matter what the hazard may be. Consider the fate of inner city schools. They must raise money locally, but anyone who can afford housing somewhere else will rather pay lower taxes somewhere else.

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By TedStevens (anonymous) | Posted August 02, 2007 at 22:41:55

We don't need better bridges, we just need more of 'em.

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By PGM (anonymous) | Posted August 02, 2007 at 23:55:20

One interesting problem with turning over this sort of thing to local governments is when bridges span from one to another; they do this around here (Pittsburgh, PA) with a fair amount of regularity in part due to all the water crossings (and I cannot imagine that two local governments wrangling over infrastructure repair would be any better than one wrangling with itself).

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By jsh (anonymous) | Posted August 03, 2007 at 06:29:11

So in other words, the state fails miserably. If you look at road deaths and injuries, the state has a terrible track record.

The solution is to privatize.

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By Joe (registered) | Posted August 03, 2007 at 10:13:10

I find it interesting that the bridge, now 40 years old, was inspected once some time in the 1980s and then inspected TWICE in the past three years (according to Pawlenty the Clown in the news conference following the tragedy). Makes me think they may have recently saw potential for a problem and tried to glaze over it with a superficial fix (the surface work that was being done at the time of the collapse).

Perhaps nothing has been done because we were all supposed to be commuting in flying cars by now....

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By w willy (registered) | Posted August 03, 2007 at 12:50:22

Much as the public hearings on the Concorde viaduct in Laval have shown, one problem is the foolhardy investment in new roads is starving proper maintenance of existing infrastructures. Citizens continue to reward politicians with votes for putting in new, and probably environmentally ill-advised, road infrastructure, but then refuse to pay taxes commensurate with the upkeep of existing roads. It is a bit like at McMaster where big donations are used to build new buildings, but then the operating and upkeep costs of those buildings come out of an unchanged operating budget, reducing teaching resources in the process.

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By Diomede (anonymous) | Posted August 03, 2007 at 14:16:19

I am an Italian professional engineer working in USA since several years, we have a strict law for structures like bridges, and buildings.
The Chief Engineering Designer and the Chief Engineering Inspector must be registered to the Court and in case of disaster they go directely to jail, only after the investigation and only if they are not guilty they are released.

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