Arch bridge
The arch bridge is one of the basic forms of bridges in addition to the girder bridge, the frame bridge and the cable-braced structures ( suspension bridge , cable-stayed bridge, etc.).
Mainly compressive forces occur in their arch. The arch is therefore the most suitable type of structure for stones and concrete with their high compressive strength. In the abutments there are vertical forces as well as horizontal forces, which is why the arched bridge requires a suitable building site and greater effort for the foundation .
Classification
Arch bridges can be classified according to different criteria.
material
Wooden arch bridges
Wooden arch bridges are rare, not only because of the transience of the material, but also because trunks and beams are made into yoke bridges or trusses rather than into arches. An example of a wooden arch bridge on stone pillars is the Trajan's Bridge from the Roman Empire . The Kintai Bridge , which was built in Japan in the 17th century based on a Chinese model, still exists today in a form that has been renovated many times over. The Mathematical Bridge in Cambridge , England, is a little younger . The Ponte dell'Accademia in Venice has a wide wooden half-timbered arch . The Kiso no ōhashi is a modern example from Japan, the Montmorency Bridge one from Quebec , Canada .
Stone arch bridges
Stone arch bridges consist of more or less carefully hewn stone , the inside often only of quarry stone . Since the wedge stones are loaded almost exclusively under pressure, the arch holds even without mortar as soon as the arch is closed, ie the keystone is set. Nevertheless, the Romans already used Opus caementicium in their bridges.
To build a stone arch bridge is usually a falsework used. The striker stones and pier heads are usually provided with a console to make it easier to set up the falsework. The Romans were already familiar with two-layer arches, in which a single-layer arch is initially built on a relatively light falsework, which then serves as falsework for the second layer and the rest of the bridge. This process was forgotten, it was only Paul Séjourné (1851–1939) who used it again in his many arched bridges.
Bridges running diagonally across a river, the vaults of which do not form a rectangle but a parallelogram , were only built in the 19th century, as they are difficult to manufacture due to the complicated geometry of the stones in the reveal. Later the vault was divided into staggered arched ribs.
Brick bridges, made entirely of brick , were built primarily for the numerous railway viaducts . The Göltzschtalbrücke is the largest bridge of its kind.
Concrete arch bridges
Concrete has properties similar to stone; it can withstand high pressure but hardly any tension and is therefore particularly suitable for arch bridges. It has already been used for stamped concrete bridges and bridges made of unreinforced concrete. Reinforced concrete arch bridges have been and are being built all over the world. The Melan construction , first a falsework made of steel with is concreted in and serves as reinforcement, enabled soon, even concrete arch bridges in the cantilever to create.
Iron and steel arch bridges
Cast iron arch bridges were the first iron bridges built after the Industrial Revolution . Cast iron has a high compressive strength, but usually a tensile strength that is four times lower and is very brittle. Cast iron bridges were therefore only built until the end of the 19th century.
The in puddling prepared wrought iron , which is more elastic than cast iron and higher withstand tensile stresses, was in the second half of the 19th century, the construction of dominant iron arch bridges material. The arches, consisting of individual rolled T-beams and soon also of double-T-beams , were created for the first time in cantilever construction with bracing. This was usually faster and cheaper than building a stone arch on a falsework.
Steel bridges were generally approved in the 1890s after initial hesitation. The high resilience of steel, both in compression and in tension, led to its use in all types of bridges, arched bridges and all other bridge forms.
CFST bridges
CFST bridges ( English concrete filled steel tube bridges ) are often built in China since 1990, large arched bridges. First, a segment arch is built from steel pipes, which are then filled with concrete. CFST bridges have spans over 200 m, including the Wushan Bridge with 460 m and the Bosideng Bridge with 530 m.
Arch shape
The arch was a long time, from the Romans to the late Middle Ages , the stone bridge dominant construction. Its circular arc line describes a complete semicircle (180 °). Its construction was based on experience long before statics began to record its properties. Even in 1913, Paul Séjourné was able to begin his great work Grandes Voûtes (Large Bridge Arches) with the sentence: Bridge arches are built from the arches built: it is a matter of experience.
The pointed arch occurs almost exclusively in bridge construction in Ottoman and Persian arch bridges.
The segment arc is, as the name suggests, a section of a circular arc, the diameter of which is larger than the clear width of the bridge. A segment arch bridge is therefore flatter than a round arch bridge, but exerts a stronger lateral thrust. Even the Romans occasionally built segment arch bridges. A very elegant segment arch bridge is the Chinese An-Ji Qiao (also called Zhaozhou Bridge) , built in 605 AD . Today they are the most common form of all arch bridges.
The basket arch is a comparatively flat arch in which the curvature increases from the apex to the abutments. Basket arches were first used in the Renaissance at the Ponte Santa Trinita , where they give the bridge a previously unattained flat profile.
The chain line describes the slack of a chain suspended at its ends. An upside-down chain line describes, in purely theoretical terms, an ideal bridge arch with a constant thickness per arch length, but which does not have to carry any other loads, such as a covering for a horizontal roadway. Since it is difficult to manufacture in practice, the theoretical meaning has almost always remained in bridge construction.
The parabola is a very similar curve to the chain line, which as an arch shape is easier to make than a chain line in practice. A parabola describes, purely theoretically, an ideal bridge arch with constant thickness for each horizontal length, but which does not have to carry any other loads, such as an overburden for a horizontal carriageway. Gustave Eiffel first used the parabolic half-timbered arch, which goes back to his partner Théophile Seyrig , for the Ponte Maria Pia , which opened in 1877 and crosses the deeply cut Douro with a large arch . Since then, the parabolic arch has been widely used in iron, steel and concrete bridges. In modern bridges, however, it is so flat that it can hardly be distinguished from a chain line or a segmented arch.
Sickle arches are two- jointed arches with two parabolas of different sizes or arcs of a circle that intersect in the joint joints . The parabolic arch of the Ponte Maria Pia can therefore also be called a sickle arch, the first Grünentaler high bridge had a sickle arch made of circular arcs .
Location of the roadway
Until the beginning of the 19th century, stone bridges had a carriageway on the arch; the space above the arch hips was solidly filled with stone material. In the larger stone arch bridges of the following time, cavities were arranged behind the initially still closed spandrels in order to save weight. The Grosvenor Bridge and the Union Arch Bridge were, if not the first, at least among the first with this construction. Regular savings sheets were later inserted there, which can be clearly seen in the open spandrels of the Max Joseph Bridge .
Following Eiffel's Ponte Maria Pia, the bridge that is found everywhere today with an elevated carriageway on top prevailed. The suspended carriageway is arranged approximately halfway up the arch and partially suspended, partially elevated. The carriageway below is arranged at the height of the crossbones of the arch and completely suspended. Nevertheless, one speaks of an arch bridge and not of a suspension bridge. The viaducts have overhead lanes on mostly narrow, massive round arches.
Elevated roadway
Suspended track
Roadway below
viaduct
design type
Uniform arch - double arch - arch ribs
For centuries, the uniform arch built on a falsework was the load-bearing element in stone bridge construction. When the spans became larger in the 19th century, the falsework also became larger, more demanding and more expensive. At the Adolphe Bridge, Paul Séjourné first divided it into two narrow double arches, which were erected one after the other on the same narrow and therefore much cheaper falsework. The reinforced concrete deck slab on top of saving arches covers the space between the two arches.
This frequently repeated type of bridge was soon further developed for concrete bridges into bridges with two or, if the width of the roadway requires, more arched ribs with slender supports and an elevated roadway slab, often made of prestressed concrete . The Colorado Street Bridge is an elegant example.
Robert Maillart developed the arch bridge into a three-hinged box girder that unites the arch, the deck and the side cheeks into one structure . Christian Menn continued the idea of a polygonal arch bridge with an elevated prestressed concrete track, which he z. B. realized at the Cascella and Nanin bridges in the south of the San Bernardino pass .
Truss arch
Since Eiffel's Ponte Maria Pia, iron and steel arch bridges have been built from half-timbered houses. Famous examples are the Hell Gate Bridge , Sydney Harbor Bridge, and Bayonne Bridge . Special cases are e.g. B. the Soo Line High Bridge or the Crooked River High Bridge , in which the arched lower chord is connected by a framework with the significantly higher, horizontally running upper chord.
Box girder
As the span increases, massive concrete arches become heavier than would be economically and technically justifiable. That is why Eugène Freyssinet built the Pont de Saint-Pierre-du-Vauvray in 1923 with the largest span at the time with concrete arches made of box girders . In 1930 he set his record at the Pont de Plougastel (later Pont Albert-Louppe). The delicate truss arches, the struts of which had to be fastened with thousands of rivets or bolts , gradually became uneconomical , with labor costs rising faster than the cost of materials . They were therefore replaced by the box girder. The Rainbow Bridge below Niagara Falls was one of the first arch bridges with large arches made of hollow steel girders.
From a static point of view
From a static point of view, arches can be firmly clamped at both ends and then three times statically indeterminate . They can be articulated ( two- hinge arch ) and simply statically indeterminate or have a third joint in the vertex ( three- hinge arch ) and be statically determined.
According to the cantilever theory, historical stone arch bridges would all be statically indeterminate in three ways if the rules of the structural analysis developed in the 19th century were applied to them. Due to the numerous masonry joints, however, they have an inner mobility that cannot be grasped with these simple terms.
In 1908 Emil Mörsch laid the foundations for integral concrete bridges with the Gmündertobel Bridge in the Swiss canton of Appenzell Ausserrhoden , the structural parts of which are connected to form monolithic structures.
Way of erection
For a long time, stone and concrete arch bridges were built on falsework , originally made of wood and later of steel. With the Melan construction method , the steel arch initially erected served as reinforcement and at the same time as formwork support for the concrete arch.
When the Eads Bridge (1874) was built over the Mississippi River , falsework was not allowed due to shipping. The bridge was therefore of tied-back cantilever beams in cantilever built. In a similar way, shortly thereafter, the restrained arch halves of Eiffel's Ponte Maria Pia and the Garabit Viaduct were executed until they merged in the middle to form a complete arch. The Sydney Harbor Bridge was even carried out without back bracing, only on the truss sections that had already been installed.
For the Caracas - La Guaira motorway bridges , falsework for the outer thirds of the arch ribs was simply supported on the transoms and braced from the side pillars. For the middle third, a falsework was mounted on the floor, stiffened with a drawstring and lifted into position from the tips of the arch thirds.
Numerous concrete box girders were concreted in the classic cantilever construction on bracings laid to the front in sections, or first the floor slab with self-supporting wooden teaching frames .
In the Storms River Bridge (Paul Sauer Bridge) (1956) in South Africa , Riccardo Morandi had the two halves of the arch concreted in a vertical position and then lowered to the middle of the arch and united. This method was later used on the Argentobel Bridge (1986) and is widely used in China.
Occasionally complete bridges are built on the side of the bank and then turned or lifted over the river.
False arch bridges
Langerscher beam
The Langersche beam , also called tied arch bridge , is an anchored arch bridge. With it, the laterally acting thrust of the arch is absorbed and neutralized by the roadway girder designed as a tension band. The roadway is therefore arranged at the bottom and the roadway girder must be correspondingly strong in order to be able to absorb these forces. With Langer's beams, as with the girder bridge, essentially only perpendicular loads occur in the support points. It is used in particular where the existing substrate would not withstand the pressure of the abutment of a real arch. Since it only becomes effective after the connection between the arch and the roadway girder, it cannot be created using the cantilever method. Today it is therefore usually lifted into place or floated in as a finished steel bridge girder .
Nielsen bridges
The Nielsen Bridge, which the Swedish engineer Octavius F. Nielsen had patented in 1926, is a tied arch bridge, the suspension rods of which are arranged at an angle so that they are anchored close together at the top and bottom in the arch or the girder, thus distributing the loads more evenly .
Network arch bridges
A network arch bridge is a tied arch bridge with hangers that cross several times, which results in an even more even load distribution.
Modified arched bridges
In China, in particular, the fly-bird-type arch is often used. With him, an arched bridge with a suspended roadway located approximately halfway up the arch is extended on both sides by the swinging of a bird-like struts and connected there to the roadway girder, which is designed as a drawstring. The lateral thrust of the bow is neutralized in a similar way to a Langer's beam. The Chaotianmen Yangtze Bridge is an example of this construction.
Occasionally, large truss bridges are designed as Gerber girder bridges , the suspension girder of which is a Langer beam. The Puente de las Américas over the Panama Canal is one such bridge.
Designs with arch elements
In the USA, large truss bridges were constructed as continuous girders that have both cantilever and arch bridge elements. The Julien Dubuque Bridge over the Mississippi River is known as a continuous steel-arch truss bridge with a suspended deck . The Francis Scott Key Bridge is another example
Girder bridges with curved chords
The designs used at the end of the 19th century, such as lens carriers , fish belly carriers , parabolic carriers and the semi-parabolic carriers and Schwedler carriers , which are often used in railway bridges , have curved belts; However, since their load-bearing effect is based on the framework and not on the arch and essentially only perpendicular forces occur in the support points, they are not counted as arch bridges but as girder bridges.
See also
- History of bridge building
- List of the largest arch bridges
- List of Roman bridges
- List of medieval stone bridges in Germany
Web links
Individual evidence
- ↑ Dirk Bühler: Bridge building . 2nd Edition. Deutsches Museum, Munich 2000, ISBN 978-3-940396-15-0 , p. 21 .
- ^ Fritz Leonhardt: Lectures on solid construction. Part 6: Basics of solid bridge construction. Springer, 1979, p. 30.
- ^ Morrisville – Trenton Railroad Bridge
- ↑ Paul Séjourné: Grandes Voûtes . Tôme I - VI. Imprimerie Vve Tardy-Pigelet et fils, Bourges 1913 ( limited preview in Google book search).
- ^ Gerhard Mehlhorn, Manfred Curbach (Ed.): Handbook bridges . 3. Edition. Springer-Vieweg, Wiesbaden 2014, ISBN 978-3-658-03339-2 , pp. 102 .
- ↑ Leonardo Fernández Troyano: Bridge Engineering. A global perspective . Colegio de Ingenieros de Caminos, Canales y Puentes; Thomas Telford, London 2003, ISBN 0-7277-3215-3 , pp. 285 ( limited preview in Google Book search).
- ↑ Julien Dubuque Bridge on HistoricBridges.org
- ↑ Otto Lueger (Ed.): Linsträger , Lexicon of the entire technology and its auxiliary sciences . Vol. 6, Stuttgart, Leipzig 1908, p. 171. On Zeno.org
- ↑ Otto Lueger (Ed.): Fischbauchträger Lexicon of all technology and its auxiliary sciences , Vol. 4, Stuttgart, Leipzig 1906, p. 41.