Unbuilding the Grace and Pearman Bridges
For Sparky and myself, curiosity drives passion which in turn fuels our life's engine. Our passion was capturing the story of both unbuilding the Grace (1929 - 2007) and Pearman (1966 - 2007) Bridges and discovering the unbuilders. It takes a lot of passion to track a project from July 2005 until April 2007 - rain, shine, hurricanes or moving to Singapore. We discovered the joy of discovery learning. Ken Canty opened the front door for us - then Steve Testa, Ponch Billingsley and Mickey Rogers opened many side doors. Below are the highlights of what we discovered, who we met and what we learned.
And a reminder from T.S. Eliot (East Coker from the Four Quartets)
Home is where one starts from. As we grow older The world becomes stranger, the pattern more complicated Of dead and living. Not the intense moment Isolated, with no before and after, But a lifetime burning in every moment And not the lifetime of one man only But of old stones that cannot be deciphered.
Unbuilding the Pearman Town Creek Span
First something about the bridge design. The Pearman is a cantilever bridge with a pair of cantilevers that support a central truss section. Here, the truss section is to the left of the pins while the cantilever section is to the right of the pins. After the explosive charge separates the truss section from the cantilever section, the cantilever section will remain attached to it's supporting column - with the end just suspended (in this case) over the Port Authority area. To remove the truss section, the connection to each cantilevered section will be compromised (by preliminary cuts and blasting). After the blast, the truss section (as 11 pieces) will drop into drum creek and be retrieved by a crane.
To repaire for the removal of the truss section, you start by placing buoys over each section (the white barrels on the top girders) so that you can locate the sections after they are under water. Then you drop the truss section to the left of the pins (shown on the right - under the white barrel and there is another pin about 3 feet up from the bottom.
A closer view of another V section. Note the to-be-buoy on the top left and the horizontal V girders joining the outside girders to the center of the vertical beam. The horizontal V beams have been cut (you can see a bit of light at the bottom edge of the cut in the left image ) so that they will break away when the main span is dropped.
The entire process is rather staggering - and here you can see a bit of the crane that is used to hoist workers to the top of the Pearman and for placing the buoys on the top. In addition, there are cables wrapped around many of the V joints and vertical joints.
The cables and a buoy are better seen here. Why the cables and buoys? - when the section drops into Town Creek - the white barrels will float thereby marking the location of a cable. The crane will then raise a segment by coupling to the cables wrapped around the bridge segments.
and here is another view of the barrels (22) and the cables for hoisting
This work is licensed under a Creative Commons License.
C. Frank Starmer