In a public competition in 2005, the Barcelona office of
the international firm Pedelta was awarded the opportunity
to develop the concept, and it produced a detailed design of
the bridge. The design took more than two years because
of the need to protect the environment. During that period
the riverbanks at the site were incorporated into the Natura
2000 network. As a result, the bridge had to be lengthened
so that it would span the riverbanks, which featured vegetation that would have to be protected from floods during
construction or restored afterward. The bridge would have
to cross the entire floodplain, meaning an overall length of
485.5 m and a span over the river itself of 120 m.
In addition to these environmental considerations, the city
sought to control access to the public
promenades along the riverbanks below the bridge in an effort to prevent
any degradation of the vegetation
there, which included wooded areas.
This goal, in addition to the city’s desire for a bridge that would serve as a
landmark for the northern part of the
city, heavily influenced the design.
The Pedelta team presented a
set of alternative designs that included steel and concrete box girders with variable depths and arches
for the main spans. Its preferred option, however, was a reinterpretation
of a steel structure with two king-post trusses. The direct interaction
between the design engineers, the
Ministerio de Fomento, and the other
agencies involved was of paramount importance in effectively
addressing all of the project’s issues and public concerns. The
renderings and cost estimates developed at early stages by the
design team made for efficient decision making and expedited
the overall design process.
The key design challenge was achieving a landmark qual-
ity while respecting the natural setting and adhering to a very
tight ($25 million) budget. The decision by the ministry to
select the design with king-post trusses was based on an aes-
thetic philosophy of “complex simplicity.” This contempo-
rary interpretation of the classic king-post truss would give
the bridge a unique identity that would be properly propor-
tioned with respect to the landscape. The design minimized
the quantity of materials, an approach very much in keeping
with the goals of sustainable development but often over-
looked, and the use of weathering steel would ensure a long
service life with very little maintenance.
The bridge is perceived as a powerful structure with a
clear identity, but it does not overpower the landscape. In-
stead, it interacts smoothly with its urban setting and the
environmentally protected areas. The structural forms are vi-
sually striking in a minimal and elegant way, relying on pure
curved lines that can be easily followed by the viewer and a
well-balanced composition based on symmetrical shapes.
Early in the preliminary design phase, the bridge length
was set at nearly 385 m, but to meet the environmental and
hydraulic requirements, that figure was increased to 485.5 m.
Nine continuous spans measure, west to east, 33, 46, 46, 58.2,
120, 58.2, 46, 46, and 32. 1 m (see the
figure on pages 56 and 57). The three
central spans over the river are of steel,
whereas the three approach spans on
each side are of concrete.
The use of steel over the river was
important in minimizing the effect on
the environment and reducing the risk
of flooding during construction. During construction Pedelta was asked by
the owner to redesign the approaches so as to reduce erection time and
cost. The side spans, initially designed
to be of steel, were thus redesigned
in concrete, but they maintained the
same outer geometry as in the original design.
The deck is 19. 9 m wide and has
been designed to accommodate four
traffic lanes, a central median, and two sidewalks for pedestrians and cyclists. This traffic lane configuration will be
achieved once a connection on the west side is widened; for
now, the bridge has two traffic lanes, two lanes for cyclists,
and two walkways. The bridge connects to existing roads
through a new roundabout at each end.
The 120 m long main span relies on two king-post trusses, the central part of the deck suspended from the trusses’
curved diagonal members. This suspender splits into two
branches that extend over the 58.2 m spans on either side to
create visual gateways. Since the main span has an overhead
structure above the roadway, the geometry of the curved diagonals over the 58.2 m spans was dependent on the required
vertical clearance of the bridge. A minimum 6 m vertical
clearance is provided at the bridge curb.
 Civil Engineering n o v e m b e r 2 0 1 5 0885-7024/15-0011-0056/$30.00 PER ARTICLE
BRIDGE CROSS SECTION
and cost estimates
developed at early
stages by the design
team made for
expedited the overall