Iron Bridge

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Coordinates: 50 ° 6 ′ 29 ″  N , 8 ° 40 ′ 56 ″  E

Iron Bridge
Iron Bridge
The Iron Bridge (2010)
use footbridge
Crossing of Main
place Frankfurt-Altstadt
Frankfurt-Sachsenhausen ( Main km 35.26)
construction steel cantilever bridge
overall length 173.59 m
width 5.44 m
construction time First version (“reinforced suspension bridge”): 1868–1869
Raised version (cantilever bridge): 1911–1912
location
Eiserner Steg (districts of Frankfurt am Main)
Iron Bridge

The Eiserne Steg is a pedestrian bridge over the Main in Frankfurt between the old town ( Fahrtor , Historical Museum ) and the Sachsenhausen district (Schulstrasse / Schifferstrasse, Sachsenhausen Hospital) , which has existed since 1868 . The first version was replaced in 1912 by a widened and reinforced construction, which was also raised. After the demolition in the last days of the Second World War , it was rebuilt unchanged in 1946, but raised again in 1993 for a renovation.

Iron bridge from 1868

planning

Before the Eiserne Steg was built, there were numerous petitions and discussions from the population in the then municipal authorities, who complained that the Old Bridge, as the only bridge to date, was in no way sufficient to improve communication with the southern districts and the surrounding area. In the background was the increase in population from 35,000 inhabitants around 1800 to almost 57,000 inhabitants in 1840. The entries said that the Alte Brücke could never cope with the increasing number of Fiaker trips to the train stations , the stone carts, and especially the increased beer transports . But the magistrate was stubborn about the cost of this project.

Finally, the citizens and - as is customary in Frankfurt - the traders in particular resorted to self-help and in June 1867 founded an association for the construction of an iron pedestrian bridge , which was soon only known in the news papers under its name, Eiserner Steg, which has been preserved to this day . One could acquire shares worth 100 guilders with 5% interest from a private company. After the construction costs, estimated at 120,000 guilders, have been fully repaid, the bridge should be transferred to the city free of charge.

Construction and construction

Eiserner Steg around 1905 (Sachsenhausen with the Dreikönigskirche in the background)

After this assurance of funding, the project was approved by the city council. On behalf of the Society for the Construction of an Iron Bridge at the Fahrtor , the engineer Peter Schmick designed a stiffened suspension bridge based on the ideas of Claus Koepcke . He had suggested that the links forming a chain of a wrought iron chain bridge, together with the connecting links between the chain and the walkway, be designed as solid “walls” on both sides of the bridge. Both “walls” together with the roadway formed a solid U-shaped bridge superstructure. The upper edges (straps) of the “walls” kept the parabolic shape of a traditional suspension bridge. They were divided from bank to bank into four triangular sections, the two upper corners of which met at the tips of the two pylons in the river . There, two “wall” sections were mounted on the pylons so that they could move lengthways and were connected to each other in a rotatable manner (with hinges ). Between the middle sections there was another hinge in the middle of the river . The two outer sections had externally rotatable armature bearings. The tensile force in the upper chords was diverted by chains on cast iron brackets down to the anchor points in the ground.

Two stone river pillars divided the river into a 79.69 m wide main opening and two 39.56 m wide secondary openings. The wrought-iron pylons, 6.34 m high and connected at the top by cross beams, stood on the pillars. The tops of the pylons were adorned with neo-Gothic pinnacles in 1871 .

The straight lower chords consisted of low lattice girders that were connected to each other by cross braces under the walkway. In the joint in the middle of the main opening, they were connected to the respective upper chord. Vertical and diagonal struts between the lower and upper chords (in the “walls”) formed a truss-like infill. The pavement consisted of an asphalt wooden plank surface, which was later replaced by a reinforced concrete ceiling. The walkway was 3.98 m wide between the wrought-iron railings. The lower chord of the bridge was 6.83 m above the zero level of the Main and only just above the level of the flood of 1784. On the banks, representative staircase structures with numerous balustrades made it possible to climb from the low-lying bank streets to the walkway.

Construction began in 1868 and took about a year. The iron construction was carried out by J. S. Fries Sohn . A total of around 500 tons of wrought iron were used. On September 29, 1869, the Eiserne Steg was inaugurated in the presence of Mayor Daniel Heinrich Mumm von Schwarzenstein .

Anyone who wanted to cross the bridge afterwards had to pay a cruiser as a toll . However, the number of users was higher than expected, so that the bridge was transferred to the city on January 1, 1886.

Iron bridge from 1912

The Eiserne Steg over the frozen Main in January 1914
Iron footbridge as a cantilever bridge:
details at the junction between the cantilever and suspension girders
Greek inscription on the iron bridge in Frankfurt / Main: "Sailing on the wine-colored sea to other people"

When the Osthafen was expanded and the Main was now also navigable upstream for larger barges, the low headroom of the Eiserner Steg represented a traffic obstacle. After corrosion damage was discovered and the coal transporter Walhalla got stuck on the lower edge of the bridge in 1910 , it was decided to do one Elevation and simultaneous widening. Although the external appearance was taken over unchanged for historical reasons, a completely different bridge was created, in particular by changing the load-bearing principle. This had even less in common with a suspension bridge , because it was built as a cantilever bridge.

Two each of the previous four bridge portions mutated to two outer trusses which extend over the river piers in the current ( cantilevered ). There is a gap between its ends, which is closed by a 25-meter-long beam ( hanging beam , with six lateral half-timbered fields each with a diagonal bar) placed at its ends . The pillars in the river were raised with reinforced concrete blocks, and the two main parts of the bridge were supported on them. The pylons that had become inoperative disappeared. To compensate for the weight of the cantilevers and the suspension beam, counterweights made of concrete were attached to the ends of the main beams. The northern main girder is fixed on its pillar and can be moved horizontally on the bank. The southern main girder is movably supported in both places. The connections with the suspension bracket can be rotated. Expansion joints in the pavement indicate the connection points. The upper chords are also interrupted near these points. Four short pieces of the upper chords have no load-bearing function (see marking in red in the picture opposite). They have only been omitted because the old appearance has been retained.

The sidewalk was widened to 5.44 meters. The staircase structures were adapted to the changed heights and were given a much more massive exterior. The lack of pegs at the highest points (formerly on the pylons) was heavily lamented by the population. Today there is a quote from the Odyssey on the southern part of these places (see picture opposite)

The price for this new building was around 236,000 marks . The construction work was completed in 1912.

Reconstruction (1946) and renovation (1993)

Eiserner Steg blown up in March 1945, winter 1945/46
Iron Bridge from Commerzbank Tower seen from

After the Second World War , the Eiserne Steg was one of the first bridges to be rebuilt after it had been blown up by the Wehrmacht in the last days of the war, like so many other bridges . The cost in 1946 was 220,000 Reichsmarks . Every day around 10,000 people crossed the river at this point. But increasing corrosion gnawed at the steel over the decades, and so it was finally renewed in 1993 for over 16 million DM . As a result of the construction of the Main-Danube Canal and the introduction of the European ships , the Eiserne Steg had to be raised again by 40 cm in 1969. In 1993 the bridge was completely renovated. Now it also has two elevators and is easily accessible for wheelchairs and prams. The bridge now has a bridge clearance height of 6.50 m above HSW .

The Greek motto, which spans the steel construction over the northern pillar of the river bridge, was created by the artist Hagen Bonifer for the Goethe year 1999. It is a quote from Homer's Odyssey (I, 183): ΠΛΕΩΝ ΕΠΙ ΟΙΝΟΠΑ ΠΟΝΤΟΝ ΕΠ ΑΛΛΟΘΡΟΟΥΣ ΑΝΘΡΩΠΟΥΣ ( pléōn epí oínopa pónton ep 'allothróous anthrópous , “Sailing on the dark sea to people with a different language” or “I drive across the red sea to people with a different tongue”).

environment

From 1859 to 1913, the Frankfurt (Main) runway gate of the connecting railway was located on the Eiserner Steg . Since then, the tracks have been used for freight traffic on the Frankfurt port railway . In 1945, however, the connection railway was reactivated for a short period of time due to the destruction of the Main bridges. Since 1979, the historical Frankfurt railway has been running here several weekends a year with its steam trains.

Artistic adaptations

  • Max Beckmann and Ernst Ludwig Kirchner have created paintings that have this Frankfurt landmark as their subject.
  • The iron bridge (1987) is the title of a drama by the Frankfurt-based Ernst-Jürgen Dreyer .
  • Eiserner Steg (2011) is the title of a song by Philipp Poisel that is part of the soundtrack of the Frankfurt film What a Man .
  • The idea of ​​a pedestrian bridge to connect two parts of the city was successfully resumed with the construction of the Holbeinsteg in 1990.

Others

The design of the Eiserner Steg (1912) as a cantilever bridge reminiscent of a chain bridge has similarities with the Friedrichsbrücke in Mannheim , built in 1891 and destroyed in 1945 , with the Liberty Bridge ( 1896) in Budapest , the Salzach Bridge (Laufen – Oberndorf) (1903) and the Neutor Bridge ( 1907) in Ulm .

literature

Web links

Commons : Eiserner Steg (Frankfurt am Main)  - Collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d e f Frank Donner: Eiserner Steg
  2. ^ A b c Volker Rödel: Civil engineering in Frankfurt am Main 1806–1914 . Societätsverlag, Frankfurt am Main 1983, ISBN 3-7973-0410-2 , p. 165-190 .
  3. ↑ Claus Köpcke: About the construction of a stiff suspension bridge , magazine of the architects and engineers association for the Kingdom of Hanover, 1860
  4. ↑ a b c Friedrich Heinzerling: The bridges in iron . Otto Spamer, Leipzig 1870, p. 409-417 ( full text in Google Book Search [accessed April 10, 2017]).
  5. ↑ The design was made in the Frankfurter Fuß unit , hence the measurements in meters that are crooked.
  6. ↑ According to the high water marks on the Eiserner Steg ( file: level Eiserner Steg 1.jpg ), the high water mark of 1784 was significantly below that of the Magdalen high water of 1342 and also below that of January 18, 1682, but higher than the other marks there.
  7. ↑ Directory of the bridge clearance heights / widths in the GDWS ASt Süd district (as of April 2017) ( Memento from January 15, 2015 in the Internet Archive )
  8. ↑ Florian Balke: Born to walk, ordered to look . In: Frankfurter Allgemeine Zeitung . No. 189 , August 16, 2007, p. 39 .
  9. ↑ Homer (translator: Schadewaldt ): The Odyssey . Rowohlt, 1958, p. 11 .