August 17, 2005 A short progress report
Can you image the Pearman bridge without traffic? My Sunday morning
bicycle rides were never like this - even at 7am!
Today's lesson - These guys exhibit the skills of a surgeon and dentist.
Imagine, having to remove these bridges and extract the supporting structures
with minimal disturbance. Yesterday, you saw from Sparky's photos that
the Pearman girders end up in a vertical position.
From a distance it seem like we are building
our own version of
Stonehenge.
Today I asked Pio Monsini how they did this and, as with other Testa skills,
it turns out not to be an accident but rather a detailed procedure
for dropping the girders. After the roadway between girders is
removed, the structural integrity of the girder is broken near one pair
of piers. The weakened girder then rotates down using the other cap as
the point of rotation. Eventually, the structural integrity of the attached
end is weakened sufficiently that the girder breaks loose and falls, almost
vertically. Apparently this reduces the complexity of removing the girders
as well as protecting the region around the girders
These are some of the members of our surgical team
and these are their surgical instruments
and a closer look at the shear (left)
And Pio, Ken and one of the surgeons (I later discovered through his
wife that this is Michael Hebb)
Here is a view of the Pearman caps - extending almost all the way to the
steel superstructure.
We all see the Testa guys working on the road surfaces, but unable to see
what is actually happening. Here you can see how they use their
shears and grapples to chip away at the
roadway between supporting girders. Once the between-girder
roadway has been removed, the girder can be prepared for removal and
dropped (vertically) into the sandy base under the bridge. Again,
the surgical precision of the removal operation is impressive. Note
near the middle of the image,
the relative position of the girders dropped near one of the supporting
columns of the Ravenel bridge approach. There is about 4-5 feet of
clearance between the Ravenel support and the dropped girder.
Neurosurgeons at work here!
To stabilize the segments east of the expansion joint, it is welded together
thus providing additional stability to the remaining segments.
