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Continued...
For aesthetic reasons, the main longitudinal girders are set back
from the edge of the bridge in order to make them less prominent, and the towers
are tapered to make them look taller and improve their appearance.
The unequal load effects arising from the position of the pivot
for the main deck have been countered by means of counter-weighting the shorter
section with concrete to achieve a slightly tail-heavy situation. The exact
amount of counterweight required was determined on site once the actual loading
of the completed structure had been measured.
Because maximum reliability and minimum, non-disruptive
maintenance were two of the ERYC's main requirements for the new bridge,
particular attention was given to the design of the bearings, which are
potentially vulnerable to wear and deterioration. Bennett Associates, who acted
as mechanical and electrical consultants for the project, designed a system
which only applies loadings to the main pintle bearing when the bridge is
pivoted and open to river traffic. The design also allows all hydraulic and
electrical equipment to be located on the north side of the bridge, removing the
need for hydraulic services to cross the river and minimising cable crossings.
When in position for road traffic, the main span rests on seven
bearings – two at the tail end, two on the main pivot pier and three at the nose
end. When the opening sequence is activated, the road is closed and the
following sequence of operations automatically takes place:
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