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This
footbridge is the first
phase of the replacement of an existing bridge that was first built in
1931, destroyed during the Spanish Civil War and reconstructed again in
1943. Since this bridge is too narrow and its reinforced concrete
structure doesn’t comply with the current standards, the owner, the
Diputació de Barcelona, decided to replace it in two phases. In the
first phase a new footbridge has been built downstream of the existing
deck; and in the second phase a new highway bridge will be placed
upstream of the old bridge, which will then be demolished.
Since
the footbridge links the
two main
neighbourhoods of the town, separated from each other by the river, we
looked for a solution that not only provides a connection
between
them but also a new place with privileged views over an environment
that is
starting to show some symptoms of degradation. The new structure is
intended to
stop this process. Although this is an ambitious target, its success is
based
on the idea that singular interventions have the power of functioning
as a
catalyst for improving dynamics.
In
order to achieve it, along the
footbridge two
clearly differentiated spaces have been created. One is the passing
through
space, the one that links the two opposite banks; the second one,
instead, placed
on the span that is over the low flow section of the river, is a static
one,
formed by a cantilevered platform that provides a place of rest and
observation.
This sort of piazza is at a lower level than the rest of the crossing
and its
access is via a few steps which separate both spaces. In order for the
platform
to be accessed, in that span the downstream beam takes a cranked shape
that
gives the bridge its characteristic and original form. In this way, the
design
of the bridge follows and highlights the natural asymmetry of the two
stage
river channel where the low flow section is not centred.
The
new deck is formed by two
asymmetric Corten
steel longitudinal hollow box girders linked together at bottom flanges
by
transversal beams. Over the latter a wood decking is installed to form
the
footway, which is channelled between the two girders. These, slightly
supplemented on its top, define the parapets of the crossing. The opaque configuration
of these parapets is
interrupted at the cantilevered platform, where a handrail with thin
vertical
supports has a more transparent appearance.
This
footbridge has been conceived as
a façade
structure, i.e. as a crossing that has a strong asymmetry giving more
importance to the downstream views,
turning
its back on the existing
bridge. Various elements try to emphasize this feature. First of all,
its
alignment is such that, coming from both abutments, the gap between the
new and
the old bridge increases in width, being maximum at the “piazza” span.
This “façade”
effect is further reinforced by giving the girder of the downstream
side its
cranked shape, placing the cantilevered platform over it, designing the
downstream parapet with a more transparent shape and installing the
lamp
columns of the street lighting on the upstream side.
Along the deck, in order
to highlight the
predominance of the piazza, from both abutments the width of the
footway
increases up to that span, and at the same time a slight slope places
it at the
highest point of the whole route.
Using
the girders as part of the
parapets has
the disadvantage that the structure takes a heavier aspect. In order to
compensate for this effect, the deck and the piers have been designed
such that
the supports are hidden by the shadow of the structure; this creates
the visual
effect of the footbridge flying from one abutment to the other.
Furthermore,
along the abutments, heavy concrete parapets have been conceived, so
that, in
contrast with the deck, they give the latter a more slender appearance.
On
the deck the street lighting is
solved by
means of five lamp columns placed over each one of the five supports,
which
helps to emphasize the rhythm of the structure. These lamp columns,
which have
been specially designed for this bridge, are fixed on the outer face of
the
upstream girder. Additional lamp columns with a more standard design
have been
installed on the approaches.
On
the left side bank the abutment
blocks the
continuity of the path along the river. For this reason, in order to
reverse
the degradation process this cul-de-sac place is beginning to suffer,
stairs
have been provided to connect the river bed with the footway approach
to the
footbridge. This element reinforces the dialog every bridge must
maintain with
its river, linking the two spaces it defines: the fist one is the
pre-existent space,
the one that is overcome; the second one is the new elevated space, the
one
that flies over the first one, linking both margins.
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