I found that line on the resume of a metallurgical expert.

I've long been fascinated with the idea that living organisms are not the only things that age. From time to time, I've collected ancient coins, and I learned that forged coins pose a serious problem for the collector, because some of the forgers (especially those in Eastern Europe) use state of the art equipment once belonging to the KGB and its various manifestations. But there's one thing that can't be forged: when coins age, the metal changes. It crystallizes in predictable ways, and experts can tell by microscopic examination whether or not a coin is in fact 2000 years old.

Knowing that even tiny pieces of metal change simply because of aging, this morning I wondered about a heavily-used metal bridge built in Minneapolis in 1967, when standards were considerably more lax than they are today. Think about the number of cars that passed over that bridge for the past 40 years, the number of times it has been repaired and resurfaced with heavy equipment rattling away, the number of ferocious winters and scorching summers it's been through.

I'd be fatigued. Who wouldn't be? Who can blame the poor bridge, which is, after all only as strong as the metal supports holding it together.

After reading this morning's news, I figured I'd go straight to James Lileks. After all, it's his turf. He's understandably very busy with the news frenzy, but he takes time to remember the once elegant bridge:

I've driven across this bridge every few days for thirty years. There are bridges, and there are bridges; this one had the most magnificent view of downtown available, and it's a miracle I never rear-ended anyone while gawking at the skyline, the old Stone Bridge, the Mississippi. You always felt proud to be here when you crossed that bridge, pleased to live in such a beautiful place. Didn't matter if it was summer twilight or hard cold winter noon - Minneapolis always seemed to be standing at attention, posing for a formal portrait . We'll have that view again - but it'll take a generation before it's no longer tinged with regret and remembrance.

According to the Star Tribune, the bridge was labeled "structurally deficient" in 2005. It didn't take much time for the Times in London to elaborate, in a very grim report:

The 40-year-old bridge that collapsed in Minnesota last night, causing the deaths of at least seven people, was graded "structurally deficient" two years ago but was not scheduled to be replaced until 2020.

Bridge 9340 was of a design known as a "non-redundant structure" by civil engineers, meaning that if a single part failed, the whole structure could collapse. It was completed before fundamental reform of bridge safety in America in the late 1960s.

In 1967, the year of its completion, another non-redundant bridge, the Silver Bridge in Ohio, fell into the river below because of the failure of a single chain link.

Forty-six people died and the disaster, like the Ronan Point tower block collapse in London the following year, prompted a period of greater caution in structural design.

The reforms came too late for I-35W bridge, which was finished in 1967. It had three spans but no supporting piers, to allow barge traffic to continue on the river below. It carried Interstate 35W and 140,000 cars and trucks a day over the Mississippi River just east of downtown of Minneapolis.

Things age. Aging sucks. Perhaps the anti-aging movement should not be limited to humans.

This is hardly a Minneapolis problem. ABC News has a story featuring a gruesome picture of the collapse, just under a headline asking and answering a question on everyone's mind right now: How Safe Are America's Bridges?
Experts Say More Than a Quarter of U.S. Bridges Are Structurally Unstable.

Aging metal fatigue is obviously a serious problem, which will only get worse, because governments would rather spend their money on other things.

Material Technologies Inc., described as "an engineering, research and development company specializing in technologies to measure microscopic fractures and flaws in metal structures and monitor metal fatigue in real time" offers a few salient "facts about bridges in the U.S.":

Visual inspection is the primary method of checking bridges for possible metal fatigue and potential catastrophic failure.

One study by the Federal Highway Administration (FHWA) found that over 90% of fatigue cracks were missed with visual inspection.

Of all the methods (visual and non-visual) used to detect cracks, only Material Technologies' Electrochemical Fatigue Sensor system can determine whether the cracks are growing. EFS can determine not only whether cracks are growing but whether they are growing slowly or rapidly.

Over the past 10 years, on average, there have been one bridge failure in the U.S. every week.

According to federal data, 39% of the bridges in the U.S. are structurally deficient or functionally obsolete

Federal law mandates that bridges over 20 feet long be inspected every other year, but it does not require any particular method of inspection.

SAFETEA-LU, the federal transportation bill currently in effect, mandated that the FHWA carry out a program to identify technologies that detect growing fatigue cracks in bridges. Material Technologies' EFS is part of that program and already has been used in Pennsylvania. It also has been used in New Jersey, Massachusetts and Utah. Overseas, bridge owners in Australia, the U.K. and elsewhere have shown interest in deployment of the EFS in the near future.

Common sense suggests, though, that age combined with fatigue is a serious problem.

UPDATE: Glenn Reynolds links an excellent report at Popular Mechanics. Bottom line:

....investigators will likely find that two factors contributed to its failure: age and heavy use.

America's gross domestic product in 2006 was $13.2 trillion--we can afford to have world-class infrastructure. As a stepping-off point, we should insist that our elected representatives publicly acknowledge the risk of neglecting the bridges, roads and other essential hardware that goes into making a modern civilization. Then we should hold them accountable for setting priorities and for marshaling the requisite resources to repair our increasingly brittle society.

UPDATE: Also via Glenn Reynolds, John Hinderaker (who lives in the area) says this:

It is hard to convey to those who don't live here the astonishment of this sort of catastrophe happening on our most traveled highway.

(I shudder to think about the many aging and fatgued bridges in the Newpennsyljerseydelawaria area.)