A log bridge is a

timber bridge A timber bridge or wooden bridge is a bridge that uses timber or wood as its principal structural material. One of the first forms of bridge, those of timber have been used since ancient times. History The most ancient form of timber bridge is ...

that uses logs that fall naturally or are intentionally felled or placed across streams. The first man-made

bridge A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somethi ...

s with significant span were probably intentionally felled

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

s. The use of emplaced logs is now sometimes used in temporary bridges used for

logging Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars. Logging is the beginning of a supply chain ...

roads, where a forest tract is to be harvested and the road then abandoned. Such log bridges have a severely limited lifetime due to

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

contact and subsequent rot and wood-eating

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

infestation. Longer lasting log bridges may be constructed by using treated logs and/or by providing well drained footings National Parks Conference 1915, p. 59. "If we can design the abutment so that no moisture can collect under the logs the life of the bridge is materially increased." of

stone In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition, and the way in which it is formed. Rocks ...

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...

combined with regular maintenance to prevent soil infiltration. This care in construction can be seen in the French bridge illustrated below, which has well locked dry set stone

abutment An abutment is the substructure at the ends of a bridge span or dam supporting its superstructure. Single-span bridges have abutments at each end which provide vertical and lateral support for the span, as well as acting as retaining walls ...

s and a footpath leveled with boards.

Various log bridge designs

File:Log bridge - naturally fallen or man felled.jpg, Log bridge over a river in

Papua New Guinea Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...

File:Zaire Log Bridge.jpg, Log bridge in

Zaire Zaire (, ), officially the Republic of Zaire (french: République du Zaïre, link=no, ), was a Congolese state from 1971 to 1997 in Central Africa that was previously and is now again known as the Democratic Republic of the Congo. Zaire was, ...

, made of multiple parallel logs File:Crossing Nisqually River near Cougar Rock 01.jpg, Log bridge over the

Nisqually River The Nisqually River is a river in west central Washington in the United States, approximately long. It drains part of the Cascade Range southeast of Tacoma, including the southern slope of Mount Rainier, and empties into the southern end of Pu ...

, United States, made of one large log with handrail File:Schwarz - Schwarztöbeli IMG 6621.JPG, Log bridge in

Switzerland ). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...

with flattened top and handrail File:Suchá Belá, Slovenský ráj, 2012, 004.JPG, Log bridge in

Slovakia Slovakia (; sk, Slovensko ), officially the Slovak Republic ( sk, Slovenská republika, links=no ), is a landlocked country in Central Europe. It is bordered by Poland to the north, Ukraine to the east, Hungary to the south, Austria to the s ...

with additional boards on top File:Dřevěný most přes potok v Západních Tatrách.jpg, Log bridge in Slovakia with additional logs laid crosswise (a

beam bridge Beam bridges are the simplest structural forms for bridge spans supported by an abutment or pier at each end. No moments are transferred throughout the support, hence their structural type is known as '' simply supported''. The simplest beam ...

) File:Vallorcine footpath bridge 2003-12-13.jpg, Log bridge in

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

with dry set stone abutments and a footpath leveled with boards File:Tibetan log bridge.JPG, Complex

Tibet Tibet (; ''Böd''; ) is a region in East Asia, covering much of the Tibetan Plateau and spanning about . It is the traditional homeland of the Tibetan people. Also resident on the plateau are some other ethnic groups such as Monpa people, ...

an log bridge made of multiple logs (a

cantilever bridge A cantilever bridge is a bridge built using structures that project horizontally into space, supported on only one end (called cantilevers). For small footbridges, the cantilevers may be simple beam (structure), beams; however, large cantilever ...

)

External links

References

{{DEFAULTSORT:Log Bridge Bridges by structural type Beam bridges Footbridges