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An HBG Constructor's
internal joint venture - HBG Flatiron, FCI North and Interbeton
- is performing the $90 million seismic retrofit of the
Benicia-Martinez Bridge, one of five San Francisco Bay
area toll bridges to be seismically retrofitted. Heavily
traveled, the bridge originally built in 1962 carries
over 100,000 vehicles a day.
Project Features:
- The retrofit involves strengthening the 10 main
spans (6200 feet) over the Carquinez Strait by replacing
the existing steel bearings with seismic isolation
bearings, adding new tapered exterior concrete jackets
to most of the piers, adding additional drilled shafts,
and placing tie-down anchors through existing drilled
shafts.
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Completed
retrofited columns protect the Benicia-Marinez bridge
against damage in the event of an earthquake.
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As part of the seismic isolation
of the Benicia-Martinez Bridge, the existing rocker
bearings were replaced with friction pendulum bearings.
The installation of the new bearings (shown here)
will allow the bridge's substructure to move up
to six feet during an earthquake with minimal displacement
of the superstructure. |
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- The seismic isolation bearings used on the project
are the largest friction pendulum bearings ever built
at over 40,000 pounds each.
- The retrofit includes drilling 175,000 holes and
adding 1,515 tons of new structural steel members,
strengthening the existing piers with 34,000 cubic
yards of structural concrete, and drilling 9,000 linear
feet of 17-inch diameter holes down through existing
drilled shaft foundations and installing tie-down
anchors.
- The project will use 94,304 feet of high strength
reinforcing steel and 5,816 tons of standard reinforcing
steel.
- All construction materials are supplied by barges
working at high tide to avoid harming ecologically
sensitive wetlands.
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Project Related Links:
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