e-mosty December 2018 e-mosty December 2018 | Page 10

combining innovation and experience with signature
motifs to produce project-specific solutions:
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deck curvature accommodated by modification of
the simpler, less-critical infill transverse T-beam
panels (which are transversely prestressed to the
edge girders).
Total design quality – elegance in aesthetics,
structural efficiency clarity and economic
buildability.
This ensures that the most critical structural
components, with prestress and stay cable
anchorages, are produced with minimal changes to
allow for the ease of fabrication and decrease both
geometric errors and formwork cost.
My signature texturing of the concrete to visually
break up the surfaces compliments the bridge’s
flowing form and brings interest in the way light
plays on the structure, both at night as well as
during the day; a vital requirement as all parts of the
structure are highly visible and can be closely
observed.
The unusual ‘S’-shaped plan form is a response to
the available land. The constraints of location of
piers and tunnels at each end give rise to an
alignment which is fluid, moving in 3 dimensions.
With an elevation of over 40m from the valley bed
below, this gives users an experience unlike any
other bridge – excitement visually and in use.
Being on a curve, torsion is generated by the
geometry which drives the design. This is carried by
a simplified deck comprising two edge box girders
attached to the towers and interconnected with T
beams. Deck torsion is resisted by the combination
of the towers and stay system.
The deck is of precast, match cast prestressed,
segmental-concrete construction. The edge box
girders carry the stay anchorages and deck torsion
and have longitudinal prestress. The segments are
similar to maximise repetition with the extreme
The deck stiff for torsion; this also gives rise to
good bending performance and hence economises
on the number of stays, The decomposition of the
deck into edge beams and in-fill panels allow for
small precast elements which are easy to handle
and erect.
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I used twin leaves for each of the three towers to
give flexibility in a highly seismic area. The ‘Y’ form
is driven by engineering requirements on cable
clearances on the ‘S’ shaped deck, minimum deck
width and seismic performance and results in a
strong aesthetic statement.
I paid particular attention to developing tower
geometry to make the formwork for the towers
highly repetitive with multiple uses; it has simple
geometrically varying elements giving economy
even with a complex shape. I used an integral deck
tower connection to negate the need for bearings
or joints in inaccessible locations and to provide
stability for safe construction.
Figure 4: Elevation of the bridge across the valley
4/2018