A truss arch

bridge A bridge is a structure built to Span (engineering), span a physical obstacle (such as a body of water, valley, road, or railway) without blocking the path underneath. It is constructed for the purpose of providing passage over the obstacle, whi ...

combines the elements of the

truss bridge A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements, usually forming triangular units. The connected elements, typically straight, may be stressed from tension, compression, or ...

and the

arch bridge An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its structural load, loads partially into a horizontal thrust restrained by the abutments at either si ...

. The actual resolution of

force In physics, a force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. In mechanics, force makes ideas like 'pushing' or 'pulling' mathematically precise. Because the Magnitu ...

s will depend upon the bridge'

design A design is the concept or proposal for an object, process, or system. The word ''design'' refers to something that is or has been intentionally created by a thinking agent, and is sometimes used to refer to the inherent nature of something ...

. If no horizontal thrusting forces are generated, this becomes an arch-shaped truss which is essentially a bent beam – see moon bridge for an example. If horizontal thrust is generated but the

apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics) A-Bomb Abomination Absorbing Man Abraxas Abyss Abyss is the name of two characters appearing in Ameri ...

of the arch is a pin joint, this is termed as a three-hinged arch. If no hinge exists at the apex, it will normally be a two-hinged arch. In ''

The Iron Bridge The Iron Bridge is a cast iron arch bridge that crosses the River Severn in Shropshire, England. Opened in 1781, it was the first major bridge in the world to be made of cast iron. Its success inspired the widespread use of cast iron as a str ...

'' shown below, the structure of each frame emulates the kind of structure that previously had been made of

wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...

. Such a wood structure uses closely fitted beams pinned together, so the members within the frames are not free to move relative to one another, as they are in a pin-jointed truss structure that allows rotation at the pin joint. Such rigid structures (which impose bending stresses upon the elements) were further developed in the 20th century as the Vierendeel truss. Image:Iron Bridge.JPG,

, a two-hinged arch, the first cast-iron bridge and the oldest still standing on its original site Image:Garabit.jpg, Garabit Viaduct, a thrust arch type employing a

catenary In physics and geometry, a catenary ( , ) is the curve that an idealized hanging chain or wire rope, cable assumes under its own weight when supported only at its ends in a uniform gravitational field. The catenary curve has a U-like shape, ...

shape Image:Eastbound over SCB.jpg, The steel Stoney Creek Bridge carries the

Canadian Pacific Railway The Canadian Pacific Railway () , also known simply as CPR or Canadian Pacific and formerly as CP Rail (1968–1996), is a Canadian Class I railway incorporated in 1881. The railway is owned by Canadian Pacific Kansas City, Canadian Pacific Ka ...

File:Truss Bridge pg 382.jpg, Illustration of a Truss arch bridge, showing the Honeymoon Bridge over the

Niagara River The Niagara River ( ) flows north from Lake Erie to Lake Ontario, forming part of the border between Ontario, Canada, to the west, and New York, United States, to the east. The origin of the river's name is debated. Iroquoian scholar Bruce T ...

(1917)

Some bridges of this type

* Maria Pia Bridge (1877),

Gustave Eiffel Alexandre Gustave Eiffel ( , ; Bonickhausen dit Eiffel; 15 December 1832 – 27 December 1923) was a French civil engineer. A graduate of École Centrale des Arts et Manufactures, he made his name with various bridges for the French railway net ...

's pioneering two-hinge arch. * Hurricane Deck Bridge (1936), the last remaining truss-type bridge on Lake of the Ozarks in central Missouri. * I-35W Mississippi River bridge (1967) bridge that collapsed in 2007 in Minneapolis, Minnesota, USA. * Navajo Bridge and newer (1995) bridge of the same general construction, each built as unsupported cantilevers joined with a central pin.

References

Truss A truss is an assembly of ''members'' such as Beam (structure), beams, connected by ''nodes'', that creates a rigid structure. In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so ...

Truss bridges by type {{bridge-type-stub