e-mosty March 2019 Long Span and Multiple Span Bridges | Page 10

Figure 4: Elevation of the bridge
After installation of the caissons at the site the
steel shafts are filled with concrete and solid 10 m
high plinths connected with a tie-beam are cast.
Each caisson was initially built in a dry dock that had
been prepared on the European side of the strait.
After the main sections were built, the caissons were
floated by controlled flooding of the dry dock and
moved to deeper water.
At the same time the sea-bed, which comprises
Miocene mudstone, was prepared by dredging to
get a level platform.
Construction continues with the installation o f the
steel shafts that will support the tower legs. This is
done in the ‘wet dock’ as the structure sinks
deeper under the increased weight.
Then 2.5m diameter open ended steel inclusion
piles were driven into the mudstone. There are
192 piles below the European tower with lengths
up to 46 m and 165 piles below the Asian tower
with lengths of 21 m.
The piles reduce tower settlement by about 80%
and increase the lateral resistance of the
foundation in the event of ship impact or seismic
action.
However the piles are not directly connected to
the caisson foundation. Instead a 3m thick gravel
bed is placed around the head of the piles on
which the caisson is placed after controlled
immersion in water up to 45m deep.
This arrangement allows the tower to articulate by
sliding during a major seismic event.
Steel towers were selected for fast erection. They
comprise tapered box sections with a chamfered
corner.
Figure 5: Plan of tower segment
Figures 6 - 8: Renderings of the bridge. Source: 1915canakkale.com
1/2019