A
Metallurgist’s Insights Into
The Minneapolis Bridge Disaster
By Joel S. Hirschhorn
02 August, 2007
Countercurrents.org
The
incredible collapse of the Minneapolis bridge will send a message to
the nation that has been repeatedly sent for decades, but that our political
system has refused to effectively respond to. 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, than 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.
Many 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. But 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.
As a metallurgist 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 our
physical infrastructure. As just 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.
[The author can be reached
through www.delusionaldemocracy.com.]
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