Langerscher beam

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An arched bridge that is anchored in itself is called a Langerscher beam . The type of construction, also known as a tied arch bridge or reinforced beam , was invented by the Austrian Josef Langer and patented in Vienna in 1859 . It was first used in 1881 for the Ferdinand Bridge over the Mur in Graz .

Construction description

Load-bearing effect of the Langer's beam under its own weight
Geratal bridge in Bischleben

The construction consists of a combination of the load-bearing effect of a beam below (stiffening beam) and a slender arch above it , to which the beam is attached with bars. The arch is anchored in the beam, whereby the beam also acts as a tie . The arch usually has a stitch between a ninth and a sixth of its span. The number of hangers (bars) is usually between 6 and 14, although an even number is usually preferred for aesthetic reasons. Usually two parallel arches are arranged on the side of the roadway. In the case of wide lanes, however, three are also possible, in contrast to the Danube Bridge Fischerdorf there is only one arch in the middle of the bridge.

For evenly distributed loads, the Langer beam is a very economical construction due to the arch load-bearing effect; unevenly distributed loads primarily cause bending loads on the beam. It is mostly used for larger spans where the difference in height between the upper edge of the roadway and the lower edge of the construction should be as small as possible. As a rule, a Langerscher beam is made of steel.

With a span of 256 meters, the Bridge of Solidarity in Duisburg is the widest- span bridge of this type of construction in Germany. The Eider Bridge in Friedrichstadt , which was completed in 1916, is the first large tied arch bridge built in Germany .

A disadvantage of the design is that the supporting effect only after the connection of the arch formed by the bar and the bridge therefore not in the cantilever can be created. Therefore, nowadays the bridges are usually built outside of the final position and then lifted, pushed in or - in the case of river bridges - floated in as a largely finished structure , so that the traffic at the construction site only has to be interrupted for a very short time.

The Langer beam, whose load-bearing effect is based on the arched bridge principle and which only has vertical hangers or bars, is to be distinguished from the similar-looking parabolic girder , which has regular diagonal struts and whose load-bearing effect is based on the principle of the framework .

Web links

Commons : Steel Tied Arch Bridges  - Collection of images, videos and audio files

Individual evidence

  1. ↑ Udo Beuke: inland waterways, inland waterways and inland ports. (PDF; 6.6 MB) In the heart of Europe - the architecture of the bridges over the Mittelland Canal in the Hanover city line. Federal Institute for Hydraulic Engineering, Karlsruhe, archived from the original on January 20, 2015 ; accessed on August 18, 2019 .
  2. ↑ Note. From a point in time between 1900 and 1935 the newly built ring line of the Graz tram was led over this bridge, in 1920 the bridge was renamed Keplerbrücke and in 1963 it was replaced by a successor without road construction.
  3. ↑ Karsten Geißler: Bridge Construction Manual: Draft, Construction, Calculation, Evaluation and Enhancement . Wilhelm Ernst & Sohn, ISBN 978-3-433-02903-9 , p. 97
  4. ↑ Construction dictionary
  5. ^ Günter Ramberger, Franceco Aigner: Steel bridges . In: Handbook bridges. 2nd edition, Springer-Verlag, Berlin Heidelberg 2010, ISBN 978-3-642-04422-9 , p. 323
  6. ↑ Eider Bridge Friedrichstadt
  7. ↑ Sven Ewert: Bridges: The development of spans and systems . Ernst & Sohn, 2002, ISBN 3-433-01612-7 , page 128 f.