Monday, August 6, 2007

A shaky situation

Every time a layer of concrete was removed from the I-35W bridge, it would wobble, construction workers have said.

The wobble would be a consequence of load redistribution, no doubt. The removal of the weight might cause the truss system to expand something like a spring. Now if those supports had fatigue cracks, those cracks could have expanded as the support system adjusted to the load change.

If the truss system would shift so noticeably after its load was lightened and shifted, one might expect that mechanical vibration from jackhammers and big pavement pounders would contribute to the weakening of the supports.

BTW, the word wobble appears in yesterday's stories, but not the word vibration.

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