Beam bridge. The simplest beam bridge could be a stone slab or a wood plank laid across a stream.
Bridges designed for modern infrastructure will usually be constructed of steel or reinforced concrete, or a combination of both. The concrete elements may be reinforced, prestressed or post-tensioned. Because no moments are transferred, thrust, as from an arch bridge, cannot be accommodated, so leading to innovative designs, such as lenticular trusses & bow string arches, which contain the horizontal forces within the superstructure. Beam bridges are often only used for relatively short distances because, unlike truss bridges, they have no built in supports. The only supports are provided by piers. These bridges can be two logs stretched across a backyard stream and have a long board that is put on top of the logs to make a bridge. Truss bridge. Design[edit] The integral members of a truss bridge[1] The nature of a truss allows the analysis of the structure using a few assumptions and the application of Newton's laws of motion according to the branch of physics known as statics.
For purposes of analysis, trusses are assumed to be pin jointed where the straight components meet. This assumption means that members of the truss (chords, verticals and diagonals) will act only in tension or compression. A more complex analysis is required where rigid joints impose significant bending loads upon the elements, as in a Vierendeel truss. Suspension bridge. A suspension bridge is a type of bridge in which the deck (the load-bearing portion) is hung below suspension cables on vertical suspenders. Outside Tibet and Bhutan, where the first examples of this type of bridge were built in the 15th century, this type of bridge dates from the early 19th century.[3][4] Bridges without vertical suspenders have a long history in many mountainous parts of the world. This type of bridge has cables suspended between towers, plus vertical suspender cables that carry the weight of the deck below, upon which traffic crosses.
This arrangement allows the deck to be level or to arc upward for additional clearance. Like other suspension bridge types, this type often is constructed without falsework. The suspension cables must be anchored at each end of the bridge, since any load applied to the bridge is transformed into a tension in these main cables. History[edit] Precursor[edit] First[edit] Wire-cable[edit] Structural behavior[edit] Structural analysis[edit] Cable-stayed bridge.
A cable-stayed bridge has one or more towers (or pylons), from which cables support the bridge deck.
There are two major classes of cable-stayed bridges: harp and fan. In the harp or parallel design, the cables are nearly parallel so that the height of their attachment to the tower is proportional to the distance from the tower to their mounting on the deck. In the fan design, the cables all connect to or pass over the top of the towers. The fan design is structurally superior with minimum moment applied to the towers but for practical reasons the modified fan is preferred especially where many cables are necessary.
In the modified fan arrangement the cables terminate near to the top of the tower but are spaced from each other sufficiently to allow better termination, improved environmental protection, and good access to individual cables for maintenance. The cable-stayed bridge is optimal for spans longer than cantilever bridges, and shorter than suspension bridges. History[edit] Bridge. Etymology The Oxford English Dictionary traces the origin of the word bridge to an Old English word brycg, of the same meaning, derived from the hypothetical Proto-Germanic root brugjō. There are cognates in other Germanic languages.
History The first bridges were made by nature itself — as simple as a log fallen across a stream or stones in the river. The first bridges made by humans were probably spans of cut wooden logs or planks and eventually stones, using a simple support and crossbeam arrangement. The Arkadiko Bridge is one of four Mycenaean corbel arch bridges part of a former network of roads, designed to accommodate chariots, between Tiryns to Epidauros in the Peloponnese, in Greece. Although large Chinese bridges of wooden construction existed at the time of the Warring States, the oldest surviving stone bridge in China is the Zhaozhou Bridge, built from 595 to 605 AD during the Sui Dynasty. Types of bridges Bridges can be categorized in several different ways. Structure type.