Editing Suspension bridge (section)

==Variations==
===Underspanned===
In an underspanned suspension bridge, also called under-deck cable-stayed bridge,<ref>{{cite journal | url=https://cdnsciencepub.com/doi/10.1139/L08-033 | doi=10.1139/L08-033 | title=Structural behaviour and design criteria of under-deck cable-stayed bridges and combined cable-stayed bridges. Part 1: Single-span bridges | year=2008 | last1=Ruiz-Teran | first1=A. M. | last2=Aparicio | first2=A. C. | journal=Canadian Journal of Civil Engineering | volume=35 | issue=9 | pages=938–950 | hdl=10044/1/14353 | s2cid=248412344 | hdl-access=free }}</ref> the main cables hang entirely below the bridge deck, but are still anchored into the ground in a similar way to the conventional type. Very few bridges of this nature have been built, as the deck is inherently less stable than when suspended below the cables. Examples include the Pont des Bergues of 1834 designed by [[Guillaume Henri Dufour]];<ref name="Peters"/> James Smith's Micklewood Bridge;<ref name="Drewry">{{cite book |title=A Memoir of Suspension Bridges: Comprising The History of Their Origin And Progress |url=https://books.google.com/books?id=Hw8LAAAAIAAJ&pg=PR1 |last=Drewry |first=Charles Stewart |year=1832 |publisher=Longman, Rees, Orme, Brown, Green & Longman |location=London |access-date=13 June 2009 |url-status=live |archive-url=https://web.archive.org/web/20130616213647/http://books.google.com/books?id=Hw8LAAAAIAAJ&pg=PR1 |archive-date=16 June 2013 }}</ref> and a proposal by [[Robert Stevenson (civil engineer)|Robert Stevenson]] for a bridge over the River Almond near [[Edinburgh]].<ref name="Drewry"/>

[[Roebling's Delaware Aqueduct]] (begun 1847) consists of three sections supported by cables. The timber structure essentially hides the cables; and from a quick view, it is not immediately apparent that it is even a suspension bridge.

<gallery widths="200" heights="170">
File:Micklewood-bridge.png|Micklewood Bridge as illustrated by Charles Drewry, 1832
File:Squibb Park Bridge uncut jeh.jpg|[[Squibb Park Bridge]], [[Brooklyn]], built 2013
File:Chains on Clifton Suspension Bridge, Bristol.jpg|[[Eyebar]] chain cables of [[Clifton Suspension Bridge]]
File:Yichang Yangtze Highway Bridge.JPG|The [[Yichang Bridge]], a plate deck suspension bridge, over the [[Yangtze River]] in China
</gallery>

===Suspension cable types===
[[File:Höyryputkisilta Näsijärvellä vuonna 1979.jpg|thumb|A former [[steam]] [[Pipeline transport|pipeline]] suspension bridge on the [[Lake Näsijärvi]] in [[Tampere]], [[Finland]], in 1979]]

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. This not only adds strength but improves reliability (often called redundancy in engineering terms) because the failure of a few flawed strands in the hundreds used pose very little threat of failure, whereas a single bad link or [[eyebar]] can cause failure of an entire bridge. (The failure of a single eyebar was found to be the cause of the collapse of the [[Silver Bridge]] over the [[Ohio River]].) Another reason is that as spans increased, engineers were unable to lift larger chains into position, whereas wire strand cables can be formulated one by one in mid-air from a temporary walkway.

====Suspender-cable terminations====
Poured sockets are used to make a high strength, permanent cable termination. They are created by inserting the suspender wire rope (at the bridge deck supports) into the narrow end of a conical cavity which is oriented in-line with the intended direction of strain. The individual wires are splayed out inside the cone or 'capel', and the cone is then filled with molten lead-antimony-tin (Pb80Sb15Sn5) solder.<ref>T R Barnard (1959). "Winding Ropes and Guide Ropes:"   Mechanical Engineering. Coal Mining Series (2nd ed.). London: Virtue. pp. 374–375.</ref>

===Deck structure types===
Most suspension bridges have open truss structures to support the roadbed, particularly owing to the unfavorable effects of using plate girders, discovered from the [[Tacoma Narrows Bridge (1940)]] bridge collapse. In the 1960s, developments in bridge aerodynamics allowed the re-introduction of plate structures as shallow [[box girders]], first seen on the [[Severn bridge]], built 1961–1966. In the picture of the [[Yichang Bridge]], note the very sharp entry edge and sloping undergirders in the suspension bridge shown. This enables this type of construction to be used without the danger of vortex shedding and consequent aeroelastic effects, such as those that destroyed the original Tacoma Narrows bridge.