Monday, September 17, 2012

it ain't just London Bridge that's falling down

The WhiteStone Bridge has an interesting
 and contentious history.

Designed in haste and opened to traffic on April 29, 1939, it was designed a bit too quickly, it turned out.

Deficiencies required a renovation within the first year, costing tax payers more.

Three years after that in 1943 engineering mistakes had to be addressed again, this time adding 14 foot support trusses to reduce flex and oscillation.

Then it was discovered in 1988 that the extra weight of the added support trusses was causing fatigue cracks that had to be fixed while the bridge remained in service.

But the cracks kept on coming.

So in 2003 the MTA removed the heavy trusses and replaced them with fibreglass fairings to effect the same stiffening at much lighter loads.

This reduced the overall weight of the roadbed by some 6,000 tons, roughly 25% of the entire weight borne by the suspension cables. But the bridge kept on flexing under load. No wonder there were cracks.

In 2008 hydraulic dampers were installed to further reduce flex, plus new paint and lighting.

Overall, hundreds of millions of dollars have been invested in this bridge over the years, keeping it on the cutting edge of technology. Some taxpayers have complained about the neverending expense.

But a near exact design called the Tacoma Narrows Bridge in Washington State opened at the same time in 1940 and collapsed in high winds just four months later.

I’ll take the renovated Whitestone, thank you. 

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