e-mosty March 2019 Long Span and Multiple Span Bridges | Page 28

DECK SYSTEM
Cross beam depths for the South Pylon are 4.5 and
5.0 meters, while cross beam depths for the North
Pylon are 4.8 and 6.0 meters.
The horizontal dimension between the column
centerlines at the saddle elevations is 22.2 meters.
Column wall thicknesses vary between 500 mm
and 1200 mm over their height.
The Central Pylon arrangement is far more
complex when compared to the other two pylons.
Twin, longitudinally inclined columns have a
separation of 37.6 meters at the top of the pile cap
and join at approximately 100 meters above the
cap elevation.
These lower inclined columns have dimensions of
6.1 x 7 meters. A delta frame consisting of the pile
cap with two inclined pylon column legs resists
longitudinal loads applied to the pylon.
Single columns with longitudinal dimensions
varying between 14.9 and 6.1 meters extend from
the top of the delta frames to the top of the 158.9-
meter tall Central Pylon columns.
Three cross beams transversely connect the pylon
columns: two cross beams below the deck and one
cross beam near the pylon top.
As with the other two pylons, the Central Pylon
columns have a slight transverse inclination, the
horizontal dimensions between the column
centerlines at the saddle elevations is 22.2 meters,
and the column wall thicknesses vary between 500
mm and 1400 mm over their height.
Seismic reinforcement detailing is provided in
potential plastic hinge regions of pylon columns
and cross beams.
Additional safety margin is provided in design of
potential brittle failure modes including shear in
pylon columns and cross beams.
Reinforcing steel in the column legs is detailed to
accommodate seismic design demands in the
column to crossbeams joints and column to pile
cap joints.
Owner requirements include designing to the
AASHTO Seismic Design Specification and detailing
lower portions potential plastic hinge regions of
pylon columns and cross beams consistent with
the Japanese seismic detailing practices. Cross
beams of the central pylon are transversely post-
tensioned to resist demands in the column joints.
The suspended bridge deck section has a total width
of 23.8 meters consisting of an 18.8-meter wide,
four-lane motorway with and shoulders and a total
width of 23.8 meters.
There are no sidewalks. Suspenders located 22.2
meters apart transversely and 20 meters
longitudinally connect the suspended deck to the
main cables.
The suspended bridge deck section is a trapezoidal,
orthotropic steel box girder with longitudinal
stiffeners on the top and bottom plates and a
maximum depth of 3.72 meters.
The deck is longitudinally continuous for 2,494
meters between the expansion joints North
Abutment and South Pylon.
Typical girded segment lengths are 20 meters, with
other segment lengths occur near support locations
and midspan areas.
Truss diaphragms are located at typical 4-meter
intervals and at the suspenders. Plate diaphragms
are located at the North Abutment and Pylons.
As it is normal with this type of decks, the details
have been designed to minimize the effects of
fatigue on the steel.
The interior of the deck will have a de-humidification
system to eliminate the possibility of corrosion and
extend its design life.
It will also be provided with both internal and
external inspection gantries as well as access points
at regular intervals.
SUPERSTRUCTURE ARTICULATION
Articulation of the suspension bridge consists of
transverse bearings for the bridge deck at the three
pylons and the north abutment; vertical pendulum
bearings, end stoppers and expansion joints at two
ends of the deck at the south pylon and the north
abutment; and longitudinal dampers connecting the
north end of the deck with the north abutment.
The transverse bearings transfer significant lateral
wind or seismic reaction forces to the interfacing
substructures and at the same time accommodate
large longitudinal relative displacements of the deck.
The vertical pendulum bearings handle the
combination of large longitudinal displacements and
potential uplift forces at the two ends of the deck.
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