Tuesday, October 30, 2007

Maine's Innovative Penobscot Narrows Bridge

Cable-stayed bridges, in which the roadway is supported by cables running to a tower, are becoming quite common. But this cable-stayed bridge in Maine is the most advanced of this type:

1) The cables run from the deck, through the tower, and back down to the deck on the other side of the tower. It's called a cradle system, and it eliminates anchor points in the towers.

2) Each cable is made of many strands that are separated from each other, rather than wound together. This allows a single strand of the cable to be removed for inspection or replacement!

3) Each of the cables is charged with nitrogen gas to protect the strands from corrosion.

4) One of the towers houses an observation platform!

The resemblance of the towers to the Washington monument is intentional. Some of the stone used in the monument came from this area.

I wonder if the over sized cable housings limit the possible scale of this design? On a larger bridge, would the cable housings present an unacceptable aerodynamic load?

Pictures and information from NYT and Wikipedia

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