Mor Temor
Arch. Mor Temor is international Architecture firm committed to designing unique buildings and one of a kind architectural concepts.
2.17 ‘Transmar’ Floating Bridge
The results of a technical assessment and evaluation study for sea crossing system at the sea of Marmara, ‘TRANSMAR’, is comprised by series of floating bridges. The proposed crossing will be approximately 35 Km long and mainly serve for the transit traffic of heavy vehicles between the European and Asian sides of Istanbul (fig. 34). The system will be connected to highways at both ends.
‘TRANSMAR’ will also connect two airports of Istanbul by road and railway. The system will also be useful for the transport of communication cables and natural gas pipelines.
Fig. 34 ‘TRANSMAR’ will be approximately35 Kmlong.
The configuration of ‘TRANSMAR’ is based on segments of floating units supported by pretensioned tendons (fig. 35). A floating structure is chosen because of water depth of 60 m which makes conventional piled structure extremely expensive. Another reason for choosing a floating structure is the presence of a fault line behind the Princess islands. Two fixed suspension bridges would be located in the middle of the crossing to enable the passage of large ships.
A part from the central portion the height of the bridge should allow coastal ships travel freely underneath the bridge elements, i.e. about 25 meters of clear height from water is required. The height of the system in the middle part should allow the passage of large ships. The height of existing bridges in Bosporus are 65 meters above the water level, hence the minimum required air draught in the middle part of the crossing would be in exceedence of 65 meters.
Fig. 35 Floating units supported by pretensioned tendons.
As a result of preliminary configuration studies two different concepts were developed as feasible alternatives;
Configuration 1: Series of fixed leg suspension bridges. This alternative is comprised of a series of suspension bridges approximately 600 meter long and 65 meter high each. The depth of water is limited to 45 meters. The main advantage of this configuration is the resistance to wave, wind and current forces. However the cost of this configuration is expected to be unacceptably high. Furthermore, the fixed system will be prone to the adverse effects of earthquakes which are frequent in the region.
Configuration 2: Series of floating bridges (fig. 36). This configuration is comprised of three different segments.
- Causeways at both ends where the depth of water is limited.
- A fixed leg suspension bridge in the middle to allow shipping navigation.
- Series of floating bridges in between the causeways and the suspension bridge.
The main advantage of this configuration is cost and not being affected from earthquakes
The ends of the system where the depth of water is limited will be based on piled construction. As the depth increases submerged pontoons will support the system. This part of the system will allow an air draught of 25 meters with a span length of 150 meters between pontoons which is sufficient for coastal shipping. In the middle of the crossing one or two suspension bridges will be placed to allow the passage of large ships. These bridges will be approximately 65 m high with a span length at least 1 Km. The system will be modular structure with floating units 150 meter long each. The modular structure will reduce the stresses due to bending and torsion. The pontoon will be connected to seabed by using tendons with specific tension characteristics to minimise heave, sway and roll motions. This will be achieved by avoiding resonant frequencies common in the area (Strait, 2001).
Fig. 36 Series of floating bridges and fixed legs suspension bridges in the middle.
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