Covered bridge
A covered bridge (English: covered bridge ) is usually in half-timbered style built wooden bridge with a roof to protect against weather . The purpose of the covering is to protect the load-bearing wooden beams from weathering , as unprotected wooden beams weather faster. Unprotected wooden bridges must be renovated every 10 to 15 years. Usually two closed side walls are needed to cover such a bridge ; such bridges are also known as ark bridges . As covered bridges However, there are also bridges that are open on the sides.
Another reason for building covered bridges used to be that horses shy away from the rushing water and were easier to lead over almost windowless closed bridges.
Spread of construction
Covered wooden bridges were widespread in wooded areas of North America and Europe from the late Middle Ages to the late 19th century . Because of the higher loads caused by heavier vehicles, such bridges are now only built for subordinate roads as well as bicycle and footpaths.
There are still around 200 covered bridges in Europe today. In the USA , however, around 1,000 of these structures have been preserved, more than half of them in the four states of Pennsylvania , Ohio , Indiana and Vermont on the east coast, and in the state of Oregon on the west coast. It is estimated that over 14,000 such bridges once existed in the United States. There are still 400 of them in Canada. Covered bridges have rarely been built on the other continents. Exceptions are China , Japan , Indonesia and Vietnam , where some bridges are known.
Covered bridges are considered folkloric symbols in the United States . That is why bridges that do not have a wooden structure are provided with wooden walls and roofs. This panel is in English as Romantic Shelter to German Romantic guard called. The replication of covered bridges goes so far that these structures have a national classification similar to the real covered bridges .
history
After the fall of the Roman Empire, only a few stone bridges were built in the history of bridge construction. Most of the bridges were built from wood in the form of yoke bridges . In the late Middle Ages, these bridges were roofed to protect the wooden structure. Examples are the Chapel Bridge in Lucerne or the Ponte Vecchio in Bassano del Grappa in Italy . Although Renaissance architects such as Andrea Palladio or Leonardo da Vinci are known to have designs for wooden bridges with supporting structures over the roadway, these hardly seem to have been implemented.
Only towards the end of the 18th century were covered bridges built, which were no longer designed as yoke bridges, but rather had trusses made of rod polygons on the side of the roadway . These bridges had side walls to better protect the structure from the weather. Compared to yoke bridges, their larger span made them less sensitive to damage from ice drift in the water below.
In Switzerland, the buildings of the brothers Hans Ulrich and Johannes Grubenmann became more famous in the 18th century . While the first bridges were still being built with rod polygons , they switched to arched structures that were combined with trusses and hanging structures . Their bridges reached spans of up to 60 meters. The most famous building is the Schaffhausen Rhine Bridge , which was 120 m long and had only one intermediate pillar. The basis for calculating the bridges was not yet available, which is why true-to-scale models were created before the bridge was built and presented to the builders for approval. Their combined technology was then also used by the Grubenmann brothers in the construction of wide-span church roofs. The Neckar Bridge Plochingen , built by Johann Christian Adam Etzel (1743–1801; uncle of Gottlieb Christian Eberhard von Etzel ) in 1778 with a cantilever span of 70 meters, which in 1905 had to give way to the expansion of the station facilities , became known in Europe . The covered wooden bridge Forbach (Northern Black Forest) over the Murg, originally rebuilt in 1955 , originally planned and built by Otto Lindemann from 1778, with its 38 meter span is regionally referred to as the "longest cantilevered, covered and, due to its stability, drivable wooden bridge in Europe". The highest covered bridge in Europe is the Hohe Brücke between the towns of Flüeli-Ranft and Kerns in the Swiss canton of Obwalden , which spans the Grosse Melchaa at a height of around 100 meters.
In America, the first covered bridge was built in 1806 by Timothy Palmer in Philadelphia over the Schuylkill River . The wooden structure with three arches was 151 meters long. The supporting structures of covered bridges were further developed in America and led to constructions that were hardly used in Europe. For example, invented Ithiel Town named after him Town'schen Staff carrier , a wooden girder , who was composed of relatively lightweight parts and was easily adaptable to different structural lengths. By Theodore Burr was Burr-carrier developed, a combination of sheet and truss .
With the advent of railways , the bridges had to be designed for heavier loads, so more and more iron and steel were used. At first the modern materials were only used for parts of the structure, later for the whole structure. Since these materials do not require weather protection, the bridges were built without weather protection from now on.
Selected examples of covered bridges
| No. | Surname | place | country | use | Length in meters | Year of completion | image | comment |
|---|---|---|---|---|---|---|---|---|
| 1 | Chapel Bridge | Lucerne | Switzerland | pedestrian | 205 | 1365 |  |
Second longest covered bridge in Europe |
| 2 | Finstermünz wooden bridge | Nauders | Austria , Switzerland | Cyclists, pedestrians | 17th | 1472 |  |
Border bridge between Tyrol and Graubünden. |
| 3 | Ponte Vecchio | Bassano del Grappa | Italy | Cyclists, pedestrians | 58 | 1567 |  |
Joch bridge with roof built by Andrea Palladio |
| 4th | Bad Säckingen wooden bridge | Bad Säckingen , Stein | Switzerland , Germany | Cyclists, pedestrians | 207 | 16th century |  |
Longest covered bridge in Europe |
| 5 | Schaffhausen – Feuerthalen Rhine bridge | Schaffhausen | Switzerland | Road traffic | 111 | 1758 |  |
Most famous building by Hans Ulrich Grubenmann , destroyed by the French in 1799 |
| 6th | Market Street Bridge | Philadelphia | United States | Road traffic | 151 | 1805 |  |
First covered bridge in America. The wooden structure has a length of 151 m, the total length of the structure with the fore bridges was 400 m. |
| 7th | Raging Bruck'n | Precious scrap | Austria | pedestrian | 11.5 | 1816 |  |
Example of a thatched bridge. The reservoir construction shortened it 2.5 m and moved a few meters. |
| 8th | Worrall Covered Bridge | Rockingham (Vermont) | United States | Road traffic | 25th | 1870 |  |
Example of a bridge with Town's lath girder . |
| 9 | Contoocook Railroad Bridge | Contoocook (New Hampshire) | United States | railroad | 44 | 1870 |  |
Railway bridge with Town's lath girder . |
| 10 | Hartland Bridge | Hartland | Canada | Road traffic | 391 | 1901 |  |
Longest covered bridge in the world. |
| 11 | Office Bridge | Westfir ( Oregon ) | United States | Road traffic, pedestrians | 56 | 1944 |  |
Example of a covered bridge with a separate pedestrian walkway. |
Further examples from the German-speaking area
Switzerland, Liechtenstein
Covered Brüggli in Zurich, broken off in 1950
Germany
Covered footbridge south of Nossen
Austria
Gschwendmühlbrücke
literature
- Philip SC Caston: Historic Wooden Covered Bridge Trusses in Germany (PDF). In: Karl-Eugen Kurrer , Werner Lorenz , Volker Wetzk (eds.): Proceedings of the Third International Congress on Construction History . Neunplus, Berlin 2009, ISBN 978-3-936033-31-1 , pp. 329-336
Web links
- Swiss Timber Bridges - The Swiss timber bridges , bridge directory with histories and photos
Individual evidence
- ↑ Rudolf Huber, Renate Rieth (Ed.): Glossarium Artis. Volume 9: Cities / Villes / Towns. Walter de Gruyter, 2011, ISBN 978-3-11-097205-4 , p. 171.
- ^ West Montrose Covered Bridge (Kissing Bridge). (No longer available online.) Township of Woolwich, archived from the original on January 6, 2012 ; accessed on April 14, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ About Covered Bridges. In: Covered Bridges of Maryland . Jim Smedley, accessed February 11, 2013 .
- ↑ In Vietnam, for example, there is the Thanh Toan Bridge in Huế , see Thanh Toan Bridge, Hue, Vietnam on the website orientalarchitecture.com , accessed on August 25, 2019.
- ^ Romantic Shelters. In: Covered Bridges of Maryland . Jim Smedley, accessed February 11, 2013 .
- ↑ C. Ceraldi, E. Russo Ermolli: The Swiss covered bridges of eighteenth century. A special case: The bridge of Schaffhausen. (PDF; 1.1 MB) Accessed February 11, 2013 (English).
- ^ T. Bitterli: Historical bridges . An introduction. In: Schweizerischer Burgenverein (Ed.): Middle Ages . No. 4 . Schwabe, 2003, ISSN 1420-6994 , p. 105-108 ( pdf [accessed February 11, 2013]).
- ↑ Josef Killer: The works of master builders Grubenmann , doctoral thesis ETHZ , Zurich 1942 - available as PDF (27 MB) on [1] , last accessed on June 30, 2019
- ↑ A. Müller, H. Kolb: Grubenmanns bridges. (PDF; 346 kB) Tec21 , 2009, accessed on February 2, 2013 (The statement in the article that only two Grubenmann bridges still exist is incorrect.).
- ↑ Figure from 1905 available on [2] , last accessed on June 30, 2019
- ↑ see [3] , last accessed on June 30, 2019
- ^ Covered Bridge. Britannica Online Encyclopedia, accessed February 11, 2013 .
