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 SerranoProxectos SL. Coruña, Spain

ABSTRACT: This publication shows several singular urban footbridges that I’ve designed as structural ele-ments integrated as part of an urban street furniture, composed by light, slender and elegant designs. They arecable-stayed constructions made of concrete and steel, with metallic decks or concrete slabs. The pavement isin wood or concrete. Attractive and distinct, they are conceived to provide continuity to pedestrian routes, orjoining areas with heavy traffic, also having the function to define spaces, thus creating distinct landmarks.

1 A METALLIC STAYED FOOTBRIDGE INARTEIXO. CORUÑA. SPAIN

Photos 1 and 2, shows an eccentric stayed footbridgelocated in the borough of Arteixo, province of LaCoruña, in Spain.

The footbridge has a steel deck with a smooth“S” shaped design in plant, 160 meters long, withoutexpansion joints. The access ramps are composed bytwo spans of 17.50 m each side and the direct span iscomposed by two continuous spans of 30 m in length.

The extreme access ramps are supported in eccen-tric tubular pillars, 457.2 mm diameter and 20 mmthick. The central span is suspended from a set of 12eccentric ties, with a double harp form, extended fromone edge of the deck up to one inclined metallic tubularslender pylon, 609.6 mm in diameter, which is situatedon the road axis.

The deck is 3 m wide, and maintains the same crosssection throughout all the footbridge, it is composed

Photo 1.

of a eccentric steel tube, 508 mm in diameter, withmetallic cantilever beams, of variable depths, joinedat the other edge to a small metallic tube, 127 mmin diameter. Metallic diagonals were arranged tostrengthened horizontal areas with greater horizontalmoments.

The wood pavement, 200 cm wide, which is nar-rower than the board, leaves individual empty spacesat both sides, it is of ipe wood, that is very compactand has a high density.

The metal railing adds the final touch to the con-cept, extremely light in its design and executed with adifferent material, stainless steel, complementing theslenderness of the board that can only be improved bystructures with a stress ribbon typology.

Illumination has been projected to focus on thestructural vertical elements, in order to project theheight of the footbridge. In addition, the illuminationby way of LEDs has been added and fitted to the board,making the zigzagging run visible at night.

Photo 2.

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Photo 3.

Photo 4.

2 A ECCENTRIC STAYED FOOTBRIDGE“THE ROSE” IN CORUÑA SPAIN

This footbridge, see photos 3, and 4, with an attrac-tive design, crosses the Avenue of San Cristobal in laCoruña, Spain.

The curved board is completely suspended from theinner edge, because the footbridge cannot rest on thearea where the petroleum piping installation is situ-ated. The difference in the levels on the other sidemakes the support aesthetical unattractive.

The footbridge’s deck, 156 meters long, with anoval plant is suspended from a set of 44 eccentricties extended from the inner edge of the deck up totwo inclined metallic pylons, 36 meters high, in spin-dle shaped, and located in the borders of the Avenue,totally separated from the footbridge.

The balance of the pylons demanded the dispositionof two tubular counter stays post-tensioned on eachpylon anchored into the abutments and in the centralelement.

Photo 5.

The board, 3 meters wide, with a multi cellularmetallic box cross section, like a plane wing profile,has a linearly variable depth, topped by two semicir-cles of 40 and 20 cm in diameter, making it appear tobe light and slender.

The pedestrian zone, measuring 2,20 m wide and7 cm thick, is of structural reinforced concrete, linkedto the deck top sheet by metallic profiles. The roughconcrete surface was chosen deliberately to avoidfrosts, slides and the tambour effect produced bypedestrian passage along a metallic skin.

The light rail, rounds off the project, it is made ofstainless steel , so that it doesn’t rest importance to thestructure, allowing the board’s slenderness to stand out,and can only be improved by structures with a stressribbon typology.

3 THE FOOTBRIDGE “THE SAILBOAT” INCORUÑA SPAIN

The footbridge, see photos 5 and 6 with a pleasingdesign, crosses the Avenue of San Cristobal, in Spain,La Coruña, and is situated in the only available publicplot 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 ofother gas reservoirs.The significant cantilevers appearbecause the structure cannot rest on these plots andthe footbridge alignment, which is not orthogonal tothe avenue, depended on these plots location and on afuture avenue alignment.

The footbridge has a clear span of 39 meters ina straight line with a parabolic elevation, to whichtwo access metallic ramps in cantilever, 30 metersspan, are added. The design of the ramps, which isthe most significant element, is zigzag-shaped, witha 10 per cent gradient. The ramps are linked to oneanother by vertical tubular transoms, and constitute a

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Photo 6.

Vierendel beam with a linearly variable depth, havinga maximum value of 5.50 m.

The board cross section, of metallic structure, wasdesigned with a plane wing profile, like the one usedin the Rose footbridge.

The footbridge was designed with a very stiffV-shaped centre pylon in reinforced concrete. Thereare as well two pillars also made of reinforced con-crete at the beginning of the ramps. The direct span ofthe footbridge is not symmetric, it is suspended eccen-trically from the centre pylon by 6 ties, 3 on each side.A horizontal tie was designed to link the two pylonbraces on the top.

The ramps compensate the torsions with the bend-ing action on the vertical tubular transoms. Thecantilever ramps, of 30 meters of span, generate a sig-nificant traction over the board and the compressionforces in the foundation. The imbalance due to theoverloading action on one side of the central pylon isabsorbed by the bending acting over the pylon.

4 THE FOOTBRIDGE “THE SWING” INCORUÑA. SPAIN

The footbridge, see photos 7 and 8, with an elegantdesign, crosses the Avenue of Alfonso Molina, themain access route to the city, with a clear span of 57 min a straight line, to which two helix 12 m in diameterare added. The overall length is 113.55 m. The clearspan is parabolic in elevation with a rise to span ratioof 1 to 30.

The deck is of reinforced concrete, with a width of4,00 m and a thickness of 40 cm. The depth of the deckresults in a very light structure whose gracefulness canbe easily appreciated.

The access ramps are each supported on 10 steeltubes, 203 mm in diameter, which spring from a singlepoint. The direct span of the footbridge is suspendedfrom two sets of ties, arranged along two hyperbolic

Photo 7.

Photo 8.

paraboloids of outstanding beauty. These paraboloidsgive the appearance of an enveloping parabolic form,whose aspect varies considerably, depending on theviewpoint.

The ties extend from the borders of the deck upto two inclined pylons located in the centre of theAvenue, totally separate from the footbridge. Thesepylons, again, work almost completely in compres-sion, since the forces transmitted by the ties balanceeach other against the two sets of anchor ties that areaalso located along the centre line of the Avenue, form-ing a harp pattern, and are anchored to a wall. The steelpylons, are 29.50 m in length, they measure 90 cm indiameter at the base and 60 cm at the head, that istopped with a sloping plate.

5 A SMALL METALLIC FOOTBRIDGEWITH AN ECCENTRIC AND LEANEDSTRUCTURAL ARC IN ORENSE, SPAIN

Photos 9 and 10, shows a steel footbridge, situated inOrense. 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 10.

by a leaned steel eccentric arc, 229 mm in diametersuspended from the arc in the Orense side that is alsosupported on the other boarder, due to the headwaylimitations.

The deck is 2.80 meters wide. The cross section iscomposed of a steel eccentric tube, 305 mm in diam-eter, 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 isconstituted by a structural concrete slab 7 centimetersthick and 2 meters wide, linked to the decks top sheetwith steel profiles.

6 FOUR METALLIC FOOTBRIDGES WITHSLABS DECK IN COMPOSITE SECTIONS INCONCRETE AND STEEL

The deck in these footbridges was designed as acomposite section of steel and concrete, extremely

Photo 11.

Photo 12.

lightweight and slender, formed by a metallic inferiorsheet reinforced a with metallic profiles, linked to ahigher thinner slab.

6.1 Footbridge “A Xuntanza” in Oleiros. Coruña.Spain

The footbridge, see photos 11 and 12, crosses the roadwith a clear span of 26 m forming a straight line, towhich are added two helix 12 m in diameter. The deckis 2,30 m wide and 18 cm deep, resulting in a very lightstructure.

The border edges in the direct span were suspendedwith metallic bars from a polygonal tension arc, com-posed of a tube, 106 mm in diameter, with a clear spanof 27,5 m, and a rise to span ratio of 1 to 6. The accessramps 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 roadsustain the arcs. The balance of the pillars demandedthe disposition of a counter tie in each pillar.

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Photo 13.

6.2 Footbridge “Whistle” in Oleiros. La Coruña.spain

This is a very simple structure, where the employedmaterials work in a rational way, due to the lightnessof its design it was named “whistle”. See photo 13.

The deck, 18,30 m long, 2,20 m wide and 160 mmdeep, is supported in a compression arch through sevenpairs of V shaped pillars, composed by tubes 82,5 mmin diameter.

The antifunicular compression arc formed by a tube15,25 m in length and 160 mm in diameter, is embed-ded in the borders against the rocky embankments ofthe road.

6.3 Footbridge in vigo. Spain

The footbridge, see photo 14, is located on the accessroad to Vigo’s university, it has a deck with a U shapeddesign in plant, composed by two access ramps, 26,5 mlong, and a direct span of 27 m long.

The inner border of the deck is stayed by means of aset of ties in three orthogonal planes. The deck is 1,7 mwide, and has a cross section composed of an eccen-tric metallic box, with metallic cantilever beams, ofvariable depths, joined to other edge by a small metal-lic profile. The pedestrian walkway over this deck is1,5 m wide.

Two pillars were designed on the borders of the roadfrom which the footbridge was stayed. The balance ofthe pillars demanded the disposition of two counterties in each pillar.

6.4 Footbridge in Iñas. Oleiros. La Coruña. Spain

Photo 15 shows the direct span of a footbridge from aprevious project designed many years ago but builtrecently. The deck is eccentrically suspended by aleaned metallic arc with metallic bars. The deck has a

Photo 14.

Photo 15.

torsion border tube with cantilevers of variable depthsas was explained before.

7 FUTURE FOOTBRIDGE “AS, IN FERROL,CORUÑA, SPAIN

Photo 16 shows the model of a footbridge whoseproject has been recently approved by the Port Author-ity of Ferrol, this construction will be situated at theentrance-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 belocated in the available plot.The access ramps are com-posed by two spans in the Ferrol side that are 20 m inlength and another span of equal length on the oppositeshore. The central main span is 60 m long and is eccen-trically suspended from a set of ties, with a double harpform geometry. The direct span is compensated withtwo eccentric stayed spans that are 18 m in length. Theties are extended from one edge of the deck up to thetwo inclined metallic tubular slender pylons, 864 mmin diameter and 37,5 m in length.

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Photo 16.

The extreme access ramps are supported by eccen-tric tubular pillars, 609.6 mm in diameter.

The deck is 3.768 m wide, and maintains the samecross section throughout the footbridge. It is composedby an eccentric steel tube, 622 mm in diameter, withmetallic cantilever beams, of variable depth, joined atthe other edge to a small metallic tube, 146 mm indiameter. The metallic tubular diagonals 60.3 mm indiameter, were arranged along the deck

The wood pavement, 240 cm wide, that is narrowerthan the board, leaves individual empty spaces at bothsides. It is of ipe wood, that is very compact and dense.

Illumination has been projected to focus on thestructural vertical elements, in order to emphasize theheight of the footbridge. The illumination by way ofLEDs has been added and inlayed to the board, mak-ing the zigzagging run visible at night. In addition theillumination of the end ramps highlights the walkwayand invites the pedestrians to cross.

REFERENCES

González Serrano,A. 2003.Two composite archs cast in placein several layers. Revista de Obras Públicas no 3432. Pages51 to 55. Spain.

González Serrano, A et al. 1995. Construction of the twinbridges at La Croruña, Spain. FIP notes. 1995/2. Page 12.

González Serrano, A et al 2007. A metallic stayed footbridgeAgro in Arteixo, La Coruña, Spain. Revista de ObrasPúblicas. no 3474. Pages 55 to 62. Spain.

González Serrano, A et al 2007. Steel footbridge suspendedand supported in an eccentric arc in Orense. Spain.Informes de la Construcción. no 508. Vol 59.Pages 55 to59. Spain.

González Serrano,A et al. 2004.A stayed footbridgeThe Rosein Corunna, Spain. Revista de Obras Públicas. no 2004.Pages 31 to 39. Spain.

González Serrano, A. 1996. A footbridge in Corunn.,Spain.FIP notes. 1996/3. Pages 3 to 5.

González Serrano, A et al 2001. A Stayed footbridge in LaCoruña. Spain. Informes de la Construcción. no 473. Vol53.Pages 5 to 9. Spain.

González Serrano, A et al. 1999. Stayed footbridge in VigoCrosses the main access to the University. Spain. Informesde la Construcción. no 461. Vol 51.Pages 5 to 8. Spain.

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González Serrano, A. 2003. Pasarela Atirantada en LaCoruña. Armonía y esbeltez. Cauce. Revista del Colegiode Ingenieros de Caminos, Canales y Puertos. no 119. Page75. Spain.

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