Sunday, March 23, 2008

Do You Trust The Bridges You Drive Across?

Before August 1st, 2007, I would have said yes to that question. I actually never gave it a second thought. I couldn't tell you how many bridges I cross daily. There are numerous overpasses, too many to count. I work in downtown Minneapolis and cross the Mississippi on a regular basis as I frequently give a co-worker a ride home. If I use 394 for my commute, I go under the construction of a bridge being built to bring the light rail down to the new Twins Stadium, also under construction. As I watch it slowly transform I cannot help but wonder, what if?


When the 35W bridge went down the whole Twin Cities metro area was in shock for days after. The bridge was a main artery. I am sure there were many like me who wondered just how many times we had driven over that bridge throughout the years without giving it a second thought.

Why am I bringing this up now? Well, just last week another bridge of similar design was closed in St Cloud,MN. A MN DOT bridge inspection found that the gusset plates were bending in four areas. Acting transportation commissioner Bob McFarlin was lauded for acting so quickly. The bridge was being re-examined after the National Transportation and Safety Board (NTSB) called a press conference in January and announced that a design flaw in the gusset plates may have caused the collapse of the 35W bridge. They stated at the time that the exact cause had not yet been determined and that the investigation was still on-going. But, they were concerned enough with their findings to issue a warning for bridges of similar design.

That's great! Good for MN DOT, except for the fact that that particular bridge was inspected by MN DOT just days after the collapse of the 35W bridge. It was at that time, deemed safe. Now it could be argued that they didn't know that they needed to be looking at the gusset plates. Well, just what were they inspecting?

If that was not enough to make me nervous. The NTSB released photos dated June 2003 which clearly showed the gusset plates bending on the 35W bridge. The gusset plates are what is used to connect girders together in the truss structure. I don't know I am no engineer. But, if I saw something bending, a piece that basically helps hold the bridge together, I might just consider that it was under stress. Stress that might cause it to fail.

In answer to my original question, do I trust the bridges that I drive over. I would have to say, not any more.

* This article is also published at azsky13.newsvine.com

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