Changing the face of Charleston : The unbuilding of the Grace and Pearman Bridges
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Unbuilding Highlights
(Apr 10)
Meeting St. Stories
(Jul 10 2006)
East Bay Stories
(Oct 10 2006)
Drum Island Stories
(Feb 17)
Pearman Bridge Stories
(Apr 3)
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(Apr 3)
Imposions: Prep and boom
(Mar 27)
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(July 23 2006)
Unbuilding Challenges
(Mar 13)
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(Feb 20)
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(Mar 13)
Video and Sounds
(Feb 28)

September 12, 2005:
A buffet of Pearman roadway and girder unbuilding

Here is the boundary between the roadway removal and open spans - as seen from the Grace Bridge

Another view of the boundary

And there is always clean-up going on - Pio is a hands-on supervisor

A week ago I was puzzled by the work at the eastern end of the superstructure. Testa was placing the vertical channels and welding angle irons. Well here, it seems they were making what I would call a tiedown - brackets that bind the bridge girder structure to the concrete pier.

Ken Canty and I talked about this and Ken helped me to understand what is going on. If you look at the right side of the concrete support, you will see a pin the couples the steel superstructure to the concrete support. As the concrete roadway is removed the entire bridge structure loses weight - sort of a Testa-diet. The tendancy, then, is for the concrete support to rise - since for all the time since the bridge was built the concrete support has had the weight of the bridge on it.

So, if enough weight is removed from the bridge, all the stresses will be concentrated in the two coupling pins. To assist the bridges integrity, the steel superstructure is couple via the tiedown cables (see the beam that link the short beam resting on top of the transverse girder (on either side) with a similar beam under the concrete cross member.

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Attribution: C. Frank Starmer and Sparky Witte from