e-mosty March 2019 Long Span and Multiple Span Bridges | Page 29

CABLE ANCHORAGES
Subterranean gravity type anchorages are located
adjacent to both bridge abutments.
For a long span bridge, limiting the accumulated
travels at the superstructure/substructure
interfaces is essential in maintaining acceptable
service life of all the mechanical units.
The massive reinforced concrete structures have
lengths of 48 meters and heights of approximately
38 meters.
The longitudinal dampers are velocity dependent
devices effectively restraining deck movements
caused by transient load conditions while allowing
slow thermal movements.
Connections of the main cables to each of the 18-
meter long x 10-meter wide anchorage blocks
utilizes grouted post-tensioning tendons anchored
in the bottom of the blocks.
The dampers have a fuse or load limiter protecting
the interfacing structures against overloading from
rare events such as exceptionally high turbulent
wind conditions or major seismic events.
The anchorages bear directly on the underlying soil
and do not require pile foundations. Bottom
elevations of the anchorages are +14.1 for the
North Anchorage and +2.3 for the South
Abutment.
The end stoppers limit the maximum longitudinal
travels of the bridge deck, thus reducing the
displacement capacity requirements for all the
mechanical units.
Large swivel modular expansion joints are specified
to accommodate significant movements (up to
±1.3 m longitudinal relative displacements) and
meet the seismic performance requirements.
CONCLUSION
In summary, the design of this unique structure
has overcome the difficult local conditions and
tight technical requirements to produce a state-of-
the-art structure which, once constructed, will
hugely improve the communications between the
Isla Grande de Chiloe and the continent.
CABLES AND SUSPENSION SYSTEM
The main cables consist of 60 prefabricated
strands each, with 127 wires per strand. 5.4 mm
galvanized strand with a breaking strength of 1860
MPa is specified.
Each of the two cables has a total steel area of
approximately 0.17 square meters. Wrapped cable
diameters are approximately 0.52 meters.
Each cable is supported by saddles at the top of
the three pylons and two saddles within the
anchorage splay chambers.
Suspenders connect to the main cable with bolted
cable clamps at a typical longitudinal spacing of 20
meters.
Zinc coated wire rope suspenders with a tensile
strength of 1610 MPa are specified.
As it is the case with the deck, the cable will be
provided with a state-of-the-art de-humidification
system to prevent corrosion of the wires and
extend its design life.
The system will inject dry air at regular intervals
into the cable. A neoprene cover along its length
will minimize air loss.
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