Pasarela Peatonal

Palma del Río Arch Bridge, Córdoba, Spain
Francisco Millanes, Dr, Eng., Prof., University Politécnica de Madrid; President, IDEAM, S.A., Madrid, Spain; Miguel Ortega, Eng., Prof., University Europea de Madrid; Project Manager, IDEAM, S.A., Madrid, Spain and Antonio Carnerero, Dr, Eng., Prof.,
University Politécnica de Madrid, Spain. Contact: miguel.ortega@ideam.es

Abstract
The present paperdiscusses the construction of Palma del Río arch bridge, of 130 m span, recently constructed in surroundings of great landscape beauty in the south of Spain. A cable-stayed network was implemented, allowing a significant reduction in bending moments in deck and arch, which leads to structures of great slenderness and transparency. The two inclined arches are linked at the key, a very effectivedisposition to withstand out-of-plane buckling. The multiple crossings of the stays led to a complex geometric problem that has been solved satisfactorily with an innovative technical design of minimum visual impact. Keywords: bowstring; tubular arch; bridge; steel; network suspension system; hangers crossing devices.

distributions, which renders this typology susceptible to be used in extremelylight footbridges as well as road and railway bridges. Steinkjer Bridge (Fig. 1) built in Norway in 1963, with a span of 80 m, was his first project using this typology, which saw a fast development in countries like Norway, Germany, United States, and Japan. The most remarkable example is the beautiful and renowned Fehmarnsund Bridge (Fig. 2) in the Baltic Sea, a composite steel-and-concretebridge for both railway and vehicles and with a span of 248 m. Built in 1963, it still holds the world record for bowstring arch bridges.

Structural Behavior
The vertical loads of the deck of a bowstring arch are suspended by the tensioned hangers, raising the loads to the upper arch. The vertical component of the arch’s compression is transmitted to the extreme supports, and the horizontalcomponent is resisted by the tensioned lower tie.1 This typology is especially useful when the soil does not bear important horizontal reactions. The structural response against antimetric vertical loads of a bowstring with vertical hangers induces important bending moments on the arch and tie of the bridge (Fig. 3a). The network system allows for a very efficient structural response which leads to avery homogeneous hanger dimensioning—the cross section is practically the same all along the structure—as well as to the minimization of bending stresses in the arch and the tie beams (Fig. 3b). It also improves both the in-plane and out-of-plane arch buckling conditions. Both the arch and the deck are subjected practically exclusively to axial forces, thus making it possible to attain highslenderness ratios and great material economy.2

Introduction
The Network Tied Arch System In 1926, Octavius F. Nielsen patented the development of the conventional vertical-hanger typology for bowstring arches, by means of oblique steel rods, in a V-configuration, which allowed him to turn the arch into a beam-type structure in which the rods took the shear forces caused by non-antifunicular loaddistributions, dramatically reducing the bending moments in the arch and the deck. The main limitation in this system comes from the compressions which may appear in some hangers when the live loads/permanent loads ratio is too high, typical in railway bridges and in light structures. In the 1950s, the concept of network bowstring arch bridges was developed by Prof. Eng Per Tveit (Norway). In anarticle published in June 1966,1 he defined it as a system which uses “inclined hangers with multiple intersections on the arch’s plane.” By resorting to a greater complexity and a higher amount of steel in the hanger system, it very notably reduces the risk of the hangers being subjected to compression in non-symmetrical load
338 Technical Reports

Fig. 1: Steinkjer Bridge (1963)

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