| Workhorses of a Suspension Bridge
For a suspension bridge to perform its job, a massive concrete block
called an anchorage must support the tension – or pull – of
the cables and bridge deck.
Each concrete block of the new Narrows Bridge, weighing 81 million pounds,
resides on either end of the bridge and is buried more than 60 feet into
the earth.
Anchorages act as counter weights by holding the ends of the main cables.
Each cable, in turn, transfer most of the bridge’s weight into the
two concrete blocks. These workhorses boast 1.4 million pounds of reinforcing
steel and 20,000 cubic yards of concrete. The concrete yardage is enough
to cover an entire football field, end zones included, 20 feet deep.
The steel wire that ultimately is fabricated into a pair of compact 20½-inch
cables travels between the anchorages and over the Narrows until 19,000
miles of wire has made the journey. Inside each anchorage, 19 compacted
strands are separated. Each strand is manually tied down in the splay
chamber to ensure the even and safe distribution of the bridge and traffic
loads.
When the new bridge is complete, the roof of the east and west anchorages
will connect seamlessly with the bridge deck and become a part of the
State Route 16 roadway.
See glossary for more bridge engineering terms.
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Anchorages are massive concrete
structures, also called "cable anchorages" and "shore
anchors." |
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The anchorage hole is 151 feet
long, 116 feet at its widest point and 63 feet at its deepest point. |
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Each anchorage block contains
20,000 cubic yards of concrete and one million pounds of reinforcing
steel. |
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Individual cable strands – 19 per cable –
are splayed inside the anchorage to distribute the load of 25 million
pounds exerted on each 20½-inch main cable. |
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