DiscoverScroll article

A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders.

The first modern examples of this type of bridge were built in the early 19th century. Besides the bridge type most commonly called suspension bridges, covered in this article, there are other types of suspension bridges. The type covered here has cables suspended between towers, with vertical suspender cables that transfer the live and dead loads of the deck below, upon which traffic crosses. Like other suspension bridge types, this type often is constructed without the use of falsework. The suspension cables must be anchored at each end of the bridge, since any load applied to the bridge is transformed into tension in these main cables. Otherwise, the bridge will typically have two smaller spans, running between either pair of pillars and the highway, which may be supported by suspender cables or their own trusswork.

The first iron chain suspension bridge in the Western world was the Jacob's Creek Bridge (1801) in Westmoreland County, Pennsylvania, designed by inventor James Finley. Early British chain bridges included the Dryburgh Abbey Bridge (1817) and 137 m Union Bridge (1820), with spans rapidly increasing to 176 m with the Menai Bridge (1826), "the first important modern suspension bridge". The Sagar Iron Suspension Bridge with a 200 feet span (also termed Beose Bridge) was constructed near Sagar, India during 1828–1830 by Duncan Presgrave, Mint and Assay Master. The Clifton Suspension Bridge (designed in 1831, completed in 1864 with a 214 m central span), is similar to the Sagar bridge.

The first wire-cable suspension bridge was the Spider Bridge at Falls of Schuylkill (1816), a modest and temporary footbridge built following the collapse of James Finley's nearby Chain Bridge at Falls of Schuylkill (1808). The first permanent wire cable suspension bridge was Guillaume Henri Dufour's Saint Antoine Bridge in Geneva of 1823, with two 40 m spans. In the United States, the first major wire-cable suspension bridge was the Wire Bridge at Fairmount in Philadelphia, Pennsylvania. The Otto Beit Bridge (1938–1939) was the first modern suspension bridge outside the United States built with parallel wire cables.

Two towers/pillars, two suspension cables, four suspension cable anchors, multiple suspender cables, the bridge deck.

Combined with the relatively simple constraints placed upon the actual deck, that makes the suspension bridge much simpler to design and analyze than a cable-stayed bridge in which the deck is in compression.

In an underspanned suspension bridge, also called under-deck cable-stayed bridge, the main cables hang entirely below the bridge deck, but are still anchored into the ground in a similar way to the conventional type.

The main suspension cables in older bridges were often made from a chain or linked bars, but modern bridge cables are made from multiple strands of wire rope.

An example of this is the Nescio Bridge in the Netherlands, and the Roebling-designed 1904 Riegelsville suspension pedestrian bridge across the Delaware River in Pennsylvania.

Roebling Suspension Bridge (USA, 1866), then the longest wire suspension bridge in the world at 1,057 feet (322 m) main span. Brooklyn Bridge (USA, 1883), the first steel-wire suspension bridge. The first suspension bridge to have a concrete deck. Golden Gate Bridge (USA, 1937), the longest suspension bridge from 1937 to 1964. Mackinac Bridge (USA, 1957), the longest suspension bridge between anchorages in the Western hemisphere. 1915 Çanakkale Bridge (Turkey, 2022), has the longest main span of any suspension bridge in the world, crosses the Dardanelles, has a main span of 2,023 meters.

Broughton Suspension Bridge (England) was an iron chain bridge built in 1826. Peace River Suspension Bridge (Canada), which was completed in 1943, collapsed when the north anchor's soil support for the suspension bridge failed in October 1957.

Quick Facts

• The suspension cables must be anchored at each end of the bridge, since any load applied to the bridge is transformed into tension in these main cables.
• Besides the bridge type most commonly called suspension bridges, covered in this article, there are other types of suspension bridges.
• Early British chain bridges included the Dryburgh Abbey Bridge (1817) and 137 m Union Bridge (1820), with spans rapidly increasing to 176 m with the Menai Bridge (1826), "the first important modern suspension bridge".
• Roebling Suspension Bridge (USA, 1866), then the longest wire suspension bridge in the world at 1,057 feet (322 m) main span.
• In an underspanned suspension bridge, also called under-deck cable-stayed bridge, the main cables hang entirely below the bridge deck, but are still anchored into the ground in a similar way to the conventional type.

Source material: Wikipedia - "Suspension bridge". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.