Innovative footbridges used as urban furniture for our cities

Tailor Made Concrete Structures – Walraven & Stoelhorst (eds)
© 2008 Taylor & Francis Group, London, ISBN 978-0-415-47535-8
Innovative footbridges used as urban furniture for our cities for the future
A. González Serrano
Proxectos SL. Coruña, Spain
ABSTRACT: This publication shows several singular urban footbridges that I’ve designed as structural elements integrated as part of an urban street furniture, composed by light, slender and elegant designs. They are
cable-stayed constructions made of concrete and steel, with metallic decks or concrete slabs. The pavement is
in wood or concrete. Attractive and distinct, they are conceived to provide continuity to pedestrian routes, or
joining areas with heavy traffic, also having the function to define spaces, thus creating distinct landmarks.
1 A METALLIC STAYED FOOTBRIDGE IN
ARTEIXO. CORUÑA. SPAIN
Photos 1 and 2, shows an eccentric stayed footbridge
located in the borough of Arteixo, province of La
Coruña, in Spain.
The footbridge has a steel deck with a smooth
“S” shaped design in plant, 160 meters long, without
expansion joints. The access ramps are composed by
two spans of 17.50 m each side and the direct span is
composed by two continuous spans of 30 m in length.
The extreme access ramps are supported in eccentric tubular pillars, 457.2 mm diameter and 20 mm
thick. The central span is suspended from a set of 12
eccentric ties, with a double harp form, extended from
one edge of the deck up to one inclined metallic tubular
slender pylon, 609.6 mm in diameter, which is situated
on the road axis.
The deck is 3 m wide, and maintains the same cross
section throughout all the footbridge, it is composed
of a eccentric steel tube, 508 mm in diameter, with
metallic cantilever beams, of variable depths, joined
at the other edge to a small metallic tube, 127 mm
in diameter. Metallic diagonals were arranged to
strengthened horizontal areas with greater horizontal
moments.
The wood pavement, 200 cm wide, which is narrower than the board, leaves individual empty spaces
at both sides, it is of ipe wood, that is very compact
and has a high density.
The metal railing adds the final touch to the concept, extremely light in its design and executed with a
different material, stainless steel, complementing the
slenderness of the board that can only be improved by
structures with a stress ribbon typology.
Illumination has been projected to focus on the
structural vertical elements, in order to project the
height of the footbridge. In addition, the illumination
by way of LEDs has been added and fitted to the board,
making the zigzagging run visible at night.
Photo 1.
Photo 2.
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Photo 5.
Photo 3.
Photo 4.
The board, 3 meters wide, with a multi cellular
metallic box cross section, like a plane wing profile,
has a linearly variable depth, topped by two semicircles of 40 and 20 cm in diameter, making it appear to
be light and slender.
The pedestrian zone, measuring 2,20 m wide and
7 cm thick, is of structural reinforced concrete, linked
to the deck top sheet by metallic profiles. The rough
concrete surface was chosen deliberately to avoid
frosts, slides and the tambour effect produced by
pedestrian passage along a metallic skin.
The light rail, rounds off the project, it is made of
stainless steel , so that it doesn’t rest importance to the
structure, allowing the board’s slenderness to stand out,
and can only be improved by structures with a stress
ribbon typology.
2 A ECCENTRIC STAYED FOOTBRIDGE
“THE ROSE” IN CORUÑA SPAIN
3 THE FOOTBRIDGE “THE SAILBOAT” IN
CORUÑA SPAIN
This footbridge, see photos 3, and 4, with an attractive design, crosses the Avenue of San Cristobal in la
Coruña, Spain.
The curved board is completely suspended from the
inner edge, because the footbridge cannot rest on the
area where the petroleum piping installation is situated. The difference in the levels on the other side
makes the support aesthetical unattractive.
The footbridge’s deck, 156 meters long, with an
oval plant is suspended from a set of 44 eccentric
ties extended from the inner edge of the deck up to
two inclined metallic pylons, 36 meters high, in spindle shaped, and located in the borders of the Avenue,
totally separated from the footbridge.
The balance of the pylons demanded the disposition
of two tubular counter stays post-tensioned on each
pylon anchored into the abutments and in the central
element.
The footbridge, see photos 5 and 6 with a pleasing
design, crosses the Avenue of San Cristobal, in Spain,
La Coruña, and is situated in the only available public
plot which is located in the closest area to the city,
presently occupied by a petroleum pipe installation.
The lot on the other side was limited by the existence of
other gas reservoirs. The significant cantilevers appear
because the structure cannot rest on these plots and
the footbridge alignment, which is not orthogonal to
the avenue, depended on these plots location and on a
future avenue alignment.
The footbridge has a clear span of 39 meters in
a straight line with a parabolic elevation, to which
two access metallic ramps in cantilever, 30 meters
span, are added. The design of the ramps, which is
the most significant element, is zigzag-shaped, with
a 10 per cent gradient. The ramps are linked to one
another by vertical tubular transoms, and constitute a
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Photo 6.
Photo 7.
Vierendel beam with a linearly variable depth, having
a maximum value of 5.50 m.
The board cross section, of metallic structure, was
designed with a plane wing profile, like the one used
in the Rose footbridge.
The footbridge was designed with a very stiff
V-shaped centre pylon in reinforced concrete. There
are as well two pillars also made of reinforced concrete at the beginning of the ramps. The direct span of
the footbridge is not symmetric, it is suspended eccentrically from the centre pylon by 6 ties, 3 on each side.
A horizontal tie was designed to link the two pylon
braces on the top.
The ramps compensate the torsions with the bending action on the vertical tubular transoms. The
cantilever ramps, of 30 meters of span, generate a significant traction over the board and the compression
forces in the foundation. The imbalance due to the
overloading action on one side of the central pylon is
absorbed by the bending acting over the pylon.
4 THE FOOTBRIDGE “THE SWING” IN
CORUÑA. SPAIN
The footbridge, see photos 7 and 8, with an elegant
design, crosses the Avenue of Alfonso Molina, the
main access route to the city, with a clear span of 57 m
in a straight line, to which two helix 12 m in diameter
are added. The overall length is 113.55 m. The clear
span is parabolic in elevation with a rise to span ratio
of 1 to 30.
The deck is of reinforced concrete, with a width of
4,00 m and a thickness of 40 cm. The depth of the deck
results in a very light structure whose gracefulness can
be easily appreciated.
The access ramps are each supported on 10 steel
tubes, 203 mm in diameter, which spring from a single
point. The direct span of the footbridge is suspended
from two sets of ties, arranged along two hyperbolic
Photo 8.
paraboloids of outstanding beauty. These paraboloids
give the appearance of an enveloping parabolic form,
whose aspect varies considerably, depending on the
viewpoint.
The ties extend from the borders of the deck up
to two inclined pylons located in the centre of the
Avenue, totally separate from the footbridge. These
pylons, again, work almost completely in compression, since the forces transmitted by the ties balance
each other against the two sets of anchor ties that area
also located along the centre line of the Avenue, forming a harp pattern, and are anchored to a wall. The steel
pylons, are 29.50 m in length, they measure 90 cm in
diameter at the base and 60 cm at the head, that is
topped with a sloping plate.
5 A SMALL METALLIC FOOTBRIDGE
WITH AN ECCENTRIC AND LEANED
STRUCTURAL ARC IN ORENSE, SPAIN
Photos 9 and 10, shows a steel footbridge, situated in
Orense. It has a straight line deck, 26 meters long,
and a single span of 20 meters. The deck is supported
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Photo 9.
Photo 11.
Photo 10.
Photo 12.
by a leaned steel eccentric arc, 229 mm in diameter
suspended from the arc in the Orense side that is also
supported on the other boarder, due to the headway
limitations.
The deck is 2.80 meters wide. The cross section is
composed of a steel eccentric tube, 305 mm in diameter, with steel cantilever beams, of variable depths,
joined at the other edge to a small steel tube.
The pedestrian zone is narrower than the board,
leaving individual empty spaces at both sides, and is
constituted by a structural concrete slab 7 centimeters
thick and 2 meters wide, linked to the decks top sheet
with steel profiles.
lightweight and slender, formed by a metallic inferior
sheet reinforced a with metallic profiles, linked to a
higher thinner slab.
6
FOUR METALLIC FOOTBRIDGES WITH
SLABS DECK IN COMPOSITE SECTIONS IN
CONCRETE AND STEEL
The deck in these footbridges was designed as a
composite section of steel and concrete, extremely
6.1 Footbridge “A Xuntanza” in Oleiros. Coruña.
Spain
The footbridge, see photos 11 and 12, crosses the road
with a clear span of 26 m forming a straight line, to
which are added two helix 12 m in diameter. The deck
is 2,30 m wide and 18 cm deep, resulting in a very light
structure.
The border edges in the direct span were suspended
with metallic bars from a polygonal tension arc, composed of a tube, 106 mm in diameter, with a clear span
of 27,5 m, and a rise to span ratio of 1 to 6. The access
ramps are supported by several pairs of leaned pillars,
132 mm in diameter, linked together at the base.
Four pillars designed on the borders of the road
sustain the arcs. The balance of the pillars demanded
the disposition of a counter tie in each pillar.
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Photo 13.
6.2
Photo 14.
Footbridge “Whistle” in Oleiros. La Coruña.
spain
This is a very simple structure, where the employed
materials work in a rational way, due to the lightness
of its design it was named “whistle”. See photo 13.
The deck, 18,30 m long, 2,20 m wide and 160 mm
deep, is supported in a compression arch through seven
pairs of V shaped pillars, composed by tubes 82,5 mm
in diameter.
The antifunicular compression arc formed by a tube
15,25 m in length and 160 mm in diameter, is embedded in the borders against the rocky embankments of
the road.
Photo 15.
6.3
Footbridge in vigo. Spain
The footbridge, see photo 14, is located on the access
road to Vigo’s university, it has a deck with a U shaped
design in plant, composed by two access ramps, 26,5 m
long, and a direct span of 27 m long.
The inner border of the deck is stayed by means of a
set of ties in three orthogonal planes. The deck is 1,7 m
wide, and has a cross section composed of an eccentric metallic box, with metallic cantilever beams, of
variable depths, joined to other edge by a small metallic profile. The pedestrian walkway over this deck is
1,5 m wide.
Two pillars were designed on the borders of the road
from which the footbridge was stayed. The balance of
the pillars demanded the disposition of two counter
ties in each pillar.
6.4
Footbridge in Iñas. Oleiros. La Coruña. Spain
Photo 15 shows the direct span of a footbridge from a
previous project designed many years ago but built
recently. The deck is eccentrically suspended by a
leaned metallic arc with metallic bars. The deck has a
torsion border tube with cantilevers of variable depths
as was explained before.
7
FUTURE FOOTBRIDGE “AS, IN FERROL,
CORUÑA, SPAIN
Photo 16 shows the model of a footbridge whose
project has been recently approved by the Port Authority of Ferrol, this construction will be situated at the
entrance-way to the port of the city.
The footbridge will have a steel deck with a smooth
“S” shaped design in plant, 190 meters long, to be
located in the available plot.The access ramps are composed by two spans in the Ferrol side that are 20 m in
length and another span of equal length on the opposite
shore. The central main span is 60 m long and is eccentrically suspended from a set of ties, with a double harp
form geometry. The direct span is compensated with
two eccentric stayed spans that are 18 m in length. The
ties are extended from one edge of the deck up to the
two inclined metallic tubular slender pylons, 864 mm
in diameter and 37,5 m in length.
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Photo 16.
The extreme access ramps are supported by eccentric tubular pillars, 609.6 mm in diameter.
The deck is 3.768 m wide, and maintains the same
cross section throughout the footbridge. It is composed
by an eccentric steel tube, 622 mm in diameter, with
metallic cantilever beams, of variable depth, joined at
the other edge to a small metallic tube, 146 mm in
diameter. The metallic tubular diagonals 60.3 mm in
diameter, were arranged along the deck
The wood pavement, 240 cm wide, that is narrower
than the board, leaves individual empty spaces at both
sides. It is of ipe wood, that is very compact and dense.
Illumination has been projected to focus on the
structural vertical elements, in order to emphasize the
height of the footbridge. The illumination by way of
LEDs has been added and inlayed to the board, making the zigzagging run visible at night. In addition the
illumination of the end ramps highlights the walkway
and invites the pedestrians to cross.
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