Skip to comments.Some bridge failures can't be avoided
Posted on 06/13/2013 12:29:00 PM PDT by Tolerance Sucks Rocks
Thousands of U.S. bridges vulnerable to collapse. That was the headline of print edition of a CBS news story a few days after an interstate highway bridge collapsed over the Skagit River in Washington State. It was the most ominous sounding lead-in to a warning weve heard before. But are events like these signs that our nations infrastructure is really crumbing? Or is the news media responding to an illusion that America can and should be made immune to human tragedies?
Fortunately, even though a few vehicles plunged into the Skagit River, no one was killed. Nor were there any fatalities in Missouri after an overpass came crashing down a few days later. Both bridges were structurally sound. They failed after being hit by moving vehicles an over-height truck in Washington and a train in Missouri. In fact, of the 30 or so major bridge failures in the United States since 1950, almost half occurred from truck, train or boat collisions. Only a handful were the result of serious deterioration of structural members that went undetected during routine engineering inspections.
Thats a pretty impressive record when you consider there are more than 600,000 highway bridges in this country. However, some would have us believe theres a disaster waiting to happen around almost every bend. Dan McNichol said on PBS Newshour that collapses like these indicate that we have neglected our system as a whole. And in the CBS News story Barry LePatner claimed a large number of bridges in every state are really a danger to the traveling public.
McNichol is an award winning journalist. LePatner is a construction attorney. Both have published books about the engineering and construction industries. Its likely that theyve seen some bridges that are in poor shape, but the reality is their main source information is the massive national database which classifies one in nine bridges as structurally deficient.
Along with the American Society of Civil Engineers, who gave a C-plus rating to the nations bridges in their annual report, these are the kind of experts that the national news media turns to whenever theres a spectacular bridge collapse. But while they may have credentials to give worrisome flavor to the story, theyre not the people inspecting our bridges and making critical engineering judgments.
From 1986 to 1990 I worked in the bridge inspection and management branches of the Washington State Department of Transportation. During that time I inspected more than a thousand highway bridges. Many were structurally deficient. A few had posted load restrictions but none were in so poor a condition that we felt compelled to recommend their closure. Yet none of them ever made national news by collapsing under traffic loads, either.
Im also keenly aware that bridge inspectors arent perfect. They can completely miss critical flaws like those on Silver Bridge over the Ohio River that collapsed in 1967 and killed 46 people, or the Mianus River Bridge failure that claimed three lives in 1983. Both bridges came down because cracks in a single steel pin werent detected. They also became lessons for the profession that led to improvements in bridge inspection technology and protocols.
More recently, 13 people died in 2007 when an I-35 bridge in Minneapolis collapsed during rush hour traffic. According to the investigation by the National Transportation Safety Board, that failure was completely unrelated to the components that earned the bridge its structurally deficient label. The day after it failed though, John Nichols focused on that classification when he wrote in The Nation that the obsessive focus on warmaking abroad was leaving a trail of death, destruction and decay in the U.S.
The kind of fear mongering by Nichols, LePartner and McNichol parallels how President Obama is justifying new levels of government secrecy and surveillance. Last week he told us its necessary to compromise some of our privacy rights and conveniences if hes to guarantee us 100 percent security. Its as foolish an illusion as his predecessors pledge to rid the world of evil.
And the same can be said for engineering failures. In our advanced technological world they have joined natural disasters and diseases as tragedies that will always be part of the human experience.
I carefully choose the bridges I use. There are only one or two in Lowell that I think are ok.
I also try to avoid getting stuck in traffic on a bridge. Oy. All that dead weight going nowhere is a disaster just waiting to happen.
Of course, that’s still no guarantee.
You need to design them so that the failure of one pin doesn’t cause the whole structure to collapse.
It’s because they don’t have enough bigger trucks:
http://en.wikipedia.org/wiki/List_of_bridge_failures#1950-1999 lists 31 in the US (excluding pedestrian bridges, those collapsing during building or destruction and one repair that didn't involve any collapse).
10 were from vehicle impacts (8 ships, 1 truck, 1 train)
3 were from fuel fires
2 were from earthquakes
6 were from flooding
1 was from running a 180,000 pound load on a 35,000 pound limit bridge.
1 was from a tornado
That leaves 8 from structural or design failures.
> “You need to design them so that the failure of one pin doesnt cause the whole structure to collapse.”
They do now. The ones that do collapse when one detail breaks were built 50 to 100 years ago. There are a lot of them out there, though. Most of the bridge overpasses (at least in my part of the country) that were built over the Interstate system are pin-and-hanger bridges.
After trillions in stimulus spending, this should not be happening.
this cant be, Obama rebuilt all our infrastructure with the stimulus funds.
I forgot, he blew it all investing in a bunch of solar companies that are now all bankrupt. Hey, but at least Al Gore got rich before they went belly up!
Can’t spend the money on bridges. Too many hungry mouths to feed. Get with the program, you meany.
This is the worst one I remember in my lifetime:
The “Siver Bridge” in West Virginia, December 1967.
Silver Bridge, that is.