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.

Home Meeting St East Bay Drum Island Mt. PLeasant Pearman Stories Grace Stories Implosions Enginnering Insights Stories of unbuilders Learning Links Bridge Video Bridge Blog Unbuilding Archive All Unbuilding Segments Building the Ravenel Bridge Photo Essays About me

September 21 2005: Removing Stonehenge

The Problem: There are a number of supporting columns linking the Town Creek and Cooper River segments of the Pearman Bridge. How does one remove these?> The problem can be readily seen here: a group of columns and caps that have to disappear.

Rather imposing when viewed from Drum Island: looking east (left) and looking west (right)

The idea dropping one of these concrete support structures is similar to dropping a tree. The structural integrity of the lower section of each vertical column is first compromised by chipping away at the base (which has been previously marked -

Holes drilled into the inner face of each column that accepts an explosive charge that, when ignited, will push the structure in the direction of the compromised base.

Practice makes perfect. This particular support will serve two purposes. Dropping it vertically will be a test of the strategy used to drop supports in the river. In addition, dropping it vertically will provide a way to minimize the domino effect - if all the segments fall in the same direction there will be a possible domino effect which each structure leaning up against its neighbor. To reduce the risk the middle structures is dropped vertically by placing the explosive charges and then timing the ignition to simply collapse the H-shaped concrete support. The explosive charges for the east (to the right) and west (to the left) H-supports supports are placed so that the strucures will fall toward this center support. Here you can note the holes drilled up the entire length of each vertical column of the center H-support as shown here from Drum Island and from the Grace Bridge

To get to the cap on the top of the columns, a looooooong man basket is used

Here is a closer view of holes being drilled into the top cap of the central support (that will be vertically dropped)

This work is licensed under a Creative Commons License.

C. Frank Starmer