A bridge is a structure built to span a gorge, valley, road, railroad track, river, body of water, or any other physical obstacle. Designs of bridges will vary depending on the function of the bridge and the nature of the terrain where the bridge is to be constructed.
The first bridges were spans made of wooden logs or planks and eventually stones, using a simple support and crossbeam arrangement. Most of these early bridges were very poorly built and could rarely support heavy weights. It was this inadequacy which led to the development of better bridges. The arch was first used by the Roman Empire for bridges and aqueducts, some of which still stand today. These arch based bridges could stand in conditions that would damage or destroy more primitive designs.
An example is the Alcántara Bridge, built over the river Tagus, near Portugal. Most earlier bridges would have been swept away by the strong current. The Romans also used cement, which lowered the variation of strength found in natural stone. One kind of cement, called pozzolana, was made of water, lime, sand, and volcanic rock. Brick and mortar bridges were built after the Roman era, because the technology for concrete was lost and then later rediscovered.
Although large Chinese bridges existed in wooden construction since the ancient Warring States, the oldest surviving stone bridge in China is the Zhaozhou Bridge, built from 595 to 605 AD during the Sui Dynasty. This bridge is also historically significant as it is the world's oldest open-spandrel stone segmental arch bridge. European segmental arch bridges date back to at least the Alconétar Bridge (approximately 2nd century AD), while the enormous Roman era Trajan's Bridge (105 AD) featured open-spandrel segmental arches in wooden construction.
- Expand this portal.
- Select featured and good articles.
The Niagara Falls Suspension Bridge was the world's first working railway suspension bridge. It spanned 825 feet (251 m) and stood 2.5 miles (4.0 km) downstream of Niagara Falls from 1855 to 1897. Connecting Niagara Falls, Ontario to Niagara Falls, New York (the two cities assimilated the towns at the ends of the bridge by 1892), the bridge carried mixed traffic on its two decks across the Niagara River; trains crossed over the river by way of the bridge's upper deck while pedestrians and carriages used the lower. As the bridge was the result of a collaboration of two companies from two countries, it was also known by its American name, the International Suspension Bridge. The bridge had other names including the Niagara Railway Suspension Bridge and Niagara Suspension Bridge, but the most common and definitive was simply the Suspension Bridge.
The Suspension Bridge was part of Canadian politician William Hamilton Merritt's vision to promote trade within his country and with its neighbor the United States. When Merritt and company invited the engineering community to bid for the bridge project, they encountered heavy criticism. Many bridge builders, and the general public, did not believe a suspension bridge could allow the safe passage of trains. Nonetheless, the bridge companies engaged several well-known civil engineers to build and maintain the bridge. Charles Ellet, Jr. was first hired to construct the bridge. Using a line laid by a kite across the 800-foot (240 m) chasm, he built a temporary suspension bridge in 1848 as the first part of his plan. Not long after, Ellet left the project after a bitter financial dispute with the bridge companies. A three-year hiatus followed before the companies hired John Augustus Roebling to complete the project. Roebling used Ellet's bridge as scaffolding to build the double-decked bridge. By 1854 his bridge was nearly complete, and the lower deck was opened for pedestrian and carriage travel. On March 18, 1855, a fully laden passenger train drove across the upper deck at 5 miles per hour (8.0 km/h), and officially opened the completed bridge.
Kaichi Watanabe was a Japanese engineer who studied and worked in Scotland, United Kingdom during the 1880s. He was one of the first Japanese engineers who came to study in the UK. He is best known for his work with Sir John Fowler and Sir Benjamin Baker in cantilever bridge construction, notably on the Forth Rail Bridge.
Watanabe studied under Henry Dyer, the Scottish engineer associated with technical education in Japan. After obtaining a degree from the Faculty of Technology of the University of Tokyo, he studied at the University of Glasgow from 1885 and graduated with a Civil Engineering and Bachelor of Science degree, and worked as a construction foreman on the Forth Rail Bridge, which crossed the Firth of Forth in eastern Scotland in 1890.
Watanabe's image became well-known in the 1887 photograph illustrating the cantilever principle, in which he poses with Fowler and Baker, suspended between the engineers who form a cantilever structure with their arms.
Bridge types: Arch bridge, Aqueduct, Bailey bridge, Bascule bridge, Beam bridge, Box girder bridge, Cable-stayed bridge, Caisson, Cantilever bridge, Cantilever spar cable-stayed bridge, Clapper bridge, Covered bridge, Curling bridge, Drawbridge, Extradosed bridge, Folding bridge, Footbridge, Girder bridge, Inca rope bridge, Jetway, Lattice truss bridge, Log bridge, Mabey Logistic Support Bridge, Moon bridge, Plate girder bridge, Pontoon bridge, Retractable bridge, Self-anchored suspension bridge, Segmental bridge, Side-spar cable-stayed bridge, Simple suspension bridge, Skew arch bridge, Step-stone bridge, Stressed ribbon bridge, Submersible bridge, Suspension bridge, Swing bridge, Taper Suspension Bridge, Tied arch bridge, Tilt bridge, Through arch bridge, Toll bridge, Transporter bridge, Trestle, Truss arch bridge, Truss bridge, Tubular bridge, Vertical lift bridge, Viaduct, Vierendeel bridge, Weigh bridge, Zig-zag bridge
Individual bridges Contoocook Railroad Bridge, Akashi Kaikyo Bridge, Delaware Memorial Bridge, Forth Bridge, Golden Gate Bridge, Huey P. Long Bridge, Humber Bridge, Kintai Bridge, Lake Ponchartrain Causeway, Mackinac Bridge, Mike O'Callaghan - Pat Tillman Memorial Bridge, Millau Viaduct, New River Gorge Bridge, Pont de Normandie, Rion-Antirion Bridge, San Francisco - Oakland Bay Bridge (Eastern span replacement), San Mateo – Hayward Bridge, Stonecutters Bridge, Sunshine Skyway Bridge, Tacoma Narrows Bridge, Tsing Ma Bridge, Verrazano-Narrows Bridge(please expand)