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Khartoum, the capital of Sudan, is situated in a unique
location surrounding the confluence of the Blue Nile and White Nile. Tuti
Island is located directly within this confluence, in a prime position in
the heart of the city. It is presently used principally as farm land, with
some village housing, and has been identified as an area with considerable
development potential. There are no fixed links to the island, access currently
being by ferry. Tuti Bridge will provide the first road to it, as well as
forming a component of the strategic road network planned for the city.

The
bridge crosses the Blue Nile at a point where it is around 200m wide.
The river is fast flowing with large seasonal variations in level, and construction
within it can be hazardous. In keeping with its location on a prime site
in the centre of the city, the Sudan Government wanted the crossing to be
a signature bridge. Tuti Bridge was therefore designed as an elegant, modern suspension
bridge with a main span of 210 metres, which both provides the desired signature
structure and avoids construction within the river.
The suspension bridge deck is of steel/concrete composite construction,
with a reinforced concrete slab spanning longitudinally between transverse
plate girders, which themselves span 16 metres between longitudinal plate
girders. The longitudinal members are attached to the two main suspension
cables, each of which comprises nineteen 70mm diameter galvanised steel
spiral strands. The substructure is reinforced concrete, supported on bored
pile foundations which penetrate into the underlying Nubian Formation. The
large horizontal forces which are applied to the suspension cable anchorages
are resisted by vertical and raking piles, using a combination of axial
load and bending.
The principal challenge
in the design of this bridge has been to provide an economical structure,
capable of being constructed using materials and methods suited to the Khartoum
region. Particular attention has therefore been given to developing simple
structural solutions and components, using where possible materials which
can be easily obtained locally. In addition a construction method has been
developed which can be undertaken using locally available equipment and
techniques.


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