I-35W Bridge Collapse: Rush to Judgment

August 9, 2007

There seems to be a rush to judgment to find the flaws that caused the I-35W bridge to collapse in Minneapolis. The new theory—faulty steel gusset plates—strikes me as grasping at straws. Why after 40 years would faulty plates suddenly result in a catastrophic failure? Why has this never been raised before as a potential flaw in this type of bridge? As MIT metallurgist Ken Russell pointed out here recently, steel is made in huge batches, and its chemistry is carefully tested. Suddenly we discovered that this ancient batch was a bad one? Or that the designer used a wrong gauge or grade of steel?

It probably will take months for a meaningful analysis of the bridge failure to emerge. Undoubtedly, the investigators will find a frightening list of contributors to the collapse, starting with the corroded steel roller bearings already reported as deficient in 1990.

Posted by Doug Smock on August 9, 2007 | Comments (2)

Industries: Minneapolis Interstate 35 Bridge Collapse

September 14, 2007

In response to: I-35W Bridge Collapse: Rush to Judgment
student commented:

I Agree

September 4, 2007

In response to: I-35W Bridge Collapse: Rush to Judgment
H Stephenson commented:

I have looked at the wiring diagram in the University study and I have observed the video presented on TV and it was presented many times. It would seem after looking at the wire diagram of the bridge that a failure of any structural member on the bridge arch framework would cause the complete bridge to fail. The framework for the bridge road does not seem as critical. The bridge seemed to fail starting on one side since they reported (again many timse) that the bridge was displaced 50 or so feet. It would seem that the logical place to start is to figure out what would cause a single member to fail. This can be several things, material, corrosion, and rivet failure. Gussett plate failure does not seem to be a logical failure mode. Only multiple gussett plate failures would cause such a thing. The expansion bearing failing to slide would distort the structure and cause a member to fail. Finally, the bridge supports on the river banks could also cause problems if one failed. It would be interesting to know if one of our spy satellites was overhead at the time of the failure. This would provide invaluable data for the analzying engineers; or if Google Earth just happened to be mapping that area of our great country.

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