e-mosty March 2019 Long Span and Multiple Span Bridges | Page 27

Figures 7 and 8:
Central Pylon
foundations on piles
Each of the two pile caps is supported by 18 piles
to support two of the four inclined pylon columns.
Pile lengths vary between 82.5 and 86 meters for
the North Pylon, and between 50.5 meters and
54.7 meters for the Central Pylon.
Voided linkages connect the twin pile caps,
resulting in a total of 36 piles under the Central
Pylon. As with the North Pylon, the Central Pylon
pile cap has a bottom elevation of +4.5 MSL
The on-shore South Pylon pile foundations and the
abutment pile foundations also use 2.5 meter-
diameter drilled shaft foundations.
Connections between the piles and pile caps are
critical in developing sufficient resistance to
seismic and other design demands.
However, steel casings are not required for
construction or to resist design demands.
Anticipated large soil movements during the MPE
event resulted in concerns related to permanent
displacements at the South Pylon foundation.
The connection design is based on a combination
of pile casing embedment into the pile caps,
welded studs on the pile casing exteriors, and
reinforcing steel.
As a result, the South Pylon pile lengths are 60
meters long. Abutment pile lengths vary between
35 and 45 meters to resist design demands.
Pylon pile caps depths vary between 6.0 and 9.0
meters. Post-tensioning is used in addition to
reinforcing steel to resist pile cap design demands.
PYLON PILE CAPS
The North and South Pylon both use an 18-pile
arrangement to support pile caps of similar
dimensions.
PYLONS
The North and South Pylons have very similar
arrangements of two reinforced concrete columns
with a slight transverse inclination and two
transverse cross beams connecting the columns.
An arrangement of 9 piles and a solid pile cap
sections are located under each of the two pylon
columns, and a voided section of the pile cap
connects the two solid pile cap sections.
One cross beam is located directly under the
bridge deck and the other near the pylon top
elevation.
The North Pylon pile cap soffit is located above the
tidal zone with a bottom elevation of +4.5 MSL,
while the on-shore South Pylon pile cap has a
bottom elevation of +21.0 MS.
The South Pylon column heights above the pile cap
are 127.7 meters, while the North Column heights
are 182.4 meters.
In contrast, the Central Pylon pile cap consists of
two linked pile caps, each cap having similar
dimensions to the North Pylon and South Pylon
pile caps.
The column base dimensions are 5.8 meters x 5.5
meters for the South Pylon, and 7.5 meters x 6.0
meters for the North Pylon, while the top
dimensions are 5.1 meters x 5.5 meters for the
South Pylon, and 5.4 meters x 6.0 meters for the
North Pylon.
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