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