Editing Simple suspension bridge (section)

==Design==
[[File:Bridge-suspension-simple.svg|thumb|In a simple suspension bridge the deck lies on the main cables]]
[[File:Bridge-suspension-nonsimple.svg|thumb|In a suspended deck bridge the deck is carried below the main cables by vertical "suspenders"]]
[[File:Comparison_catenary_parabola.svg|thumb|Comparison of a catenary (black dotted curve) and a parabola (red solid curve) with the same span and sag. The catenary represents the profile of a simple suspension bridge, or the cable of a suspended-deck suspension bridge on which its deck and hangers have negligible mass compared to its cable. The parabola represents the profile of the cable of a suspended-deck suspension bridge on which its cable and hangers have negligible mass compared to its deck.]]

The very lightest bridges of this type consist of a single footrope and nothing more.  These are [[tightrope]]s and [[slackline]]s, and require skill to use.  More commonly, the footrope is accompanied by one or two handrail ropes, connected at intervals by vertical side ropes.  This style is used by mountaineers and is employed extensively in New Zealand on lesser backcountry walking tracks where examples are referred to as 'three wire bridges'.  A slightly heavier variation has two ropes supporting a deck, and two handrail ropes.  Handrails are necessary because these bridges are prone to oscillate side to side and end to end.  Rarely, the footrope (or footrope plus handrails) is combined with an overhead rope similar to a [[zip-line]] or [[cableway]].

In some cases, such as the [[Capilano Suspension Bridge]], the primary supports form the handrails with the deck suspended below them. This makes for more motion side-to-side in the deck than when the primary supports are at deck level, but less motion in the handrails.

Disadvantages connected with simple suspension bridges are very great.  The location of the deck is limited, massive anchorages and piers generally are required, and loading produces transient deformation of the deck.<ref name="Bovey">{{cite book
|title=Applied Mechanics
|author=Henry Taylor Bovey
|pages=150
|volume=2
|publisher=Printed by John Lovell & Son for the Office of the Minister of Agriculture, Canada
|location=Montreal
|year=1882
|url=https://books.google.com/books?id=cplBAAAAIAAJ&q=%22simple+suspension+bridge%22&pg=PA85
}} pages 85-90</ref>  Solutions to these problems led to a wide variety of methods of stiffening the deck,<ref name="Bovey" /><ref>{{cite book
|title=Bridges: an elementary treatise on their construction and history
|author=Fleeming Jenkin
|author-link=Fleeming Jenkin
|publisher=Adam and Charles Black
|location=Edinburgh
|year=1876 <!-- n.b., the book bears the date 1776 but this is an error;  per WorldCat the correct date is regarded to be 1876 -->
|pages=[https://archive.org/details/bridgesanelemen00jenkgoog/page/n68 345]
|url=https://archive.org/details/bridgesanelemen00jenkgoog
|quote=simple suspension bridge.
}} pages 304-305</ref> resulting in several other types of suspension bridge.  These include a [[stressed ribbon bridge]], which is closely related to a simple suspension bridge but has a stiffened deck suitable for vehicle traffic.

A very light bridge, constructed with cables under high tension, may approach a [[suspended deck bridge]] in the nearly horizontal grade of its deck.

The bridge may be stiffened by the addition of cables that do not bear the primary structural or live loads and so may be relatively light. These also add stability in wind.  An example is the {{convert|220|m|ft|adj=mid|-long|sp=us}} bridge across the river [[Drac (river)|Drac]] at [[Lac de Monteynard-Avignonet]]:  this bridge has stabilizing cables below and to the side of the deck.

To reduce twisting motion in response to users a bridge may employ vertical drop cables from each side at the center of the bridge, anchored to the ground below.