In a slab, the bridge is supported by a superstructure that acts as a single solid beam over the obstruction. While most commonly associated with reinforced concrete, timber can also be used.
A rare type of bridge more common in the UK are simple stone slab bridges, which consist of a single massive slab of stone that is placed between a substructure. Single span stone slab bridges are known as clam bridges. Multiple span stone slab bridges are known as clapper bridges.
Truss bridges are a form of a beam bridge, where a triangular framework of members and chords form a structure that functions as a large beam. Truss bridges are described according to the arrangement of the trusses: deck trusses below the roadway , pony trusses above the roadway, but without overhead bracing , and through trusses above the roadway, with overhead bracing. Researchers may wish to note that historically, through truss bridges were sometimes called high trusses, and pony trusses were sometimes called low trusses.
Metal truss bridges come in a wide variety of arrangements and configurations as shown below. Most of the following truss designs are adapted from those which appeared in J. Pratt Half-Hip: Some Pratt pony truss bridges lack hip vertical members, and are known as half-hip Pratt truss bridges. Howe: Diagonals follow the opposite orientation as that of the Pratt. The Pratt was more common on metal truss, while the Howe was more common on timber trusses. Pennsylvania Petit Truss: A Parker truss with subdivided panels.
Two common forms shown above. Warren With Verticals : Most Warren truss bridges display vertical members, although the frequency of the verticals can vary. Warren trusses with or without verticals were a common truss type. Polygonal Warren: Warren trusses can have polygonal top chords, much like Parker truss bridges. These are known as polygonal Warren truss bridges.
Double-Intersection Warren: This design can be thought of as two Warren trusses superimposed and offset on top of each other. K-Truss: Invented during the construction of the Quebec Bridge, the K-Truss can be arranged in several different ways, with two orientations shown above.
The top chord does not have to be polygonal. Most commonly used in the s as an early metal truss form. Queenpost: Used for very short spans.
Thacher: An archaic and rare truss form. Exact form may vary slightly, no existing examples exactly follow the design patented by Edwin Thacher. Metal truss bridges are further classified by the manner in which the members are joined together. Connections may be pinned, riveted, bolted, or welded.
Pinned connections, common from ca. Pinned connections were made obsolete by the rise of riveted connections, which offered a more rigid connection. With riveted connections, truss members were riveted to a gusset plate to connect the members. Later, rivets would be substituted for bolts or welds to fasten the members onto the gusset plates. Details for bolted and welded connections are similar to the riveted connection shown above. Wooden covered bridges are truss bridges built from timber and covered with a non-structural roof and wall system.
Underneath the roof and wall are truss members. Like metal truss bridges, covered bridges have different configuration. While there is some overlap between metal and covered truss configurations, details for truss configurations of the same name may differ between covered and metal, and there are many covered truss configurations that were not used in metal truss construction.
Also note that while the predominant material used in covered bridges is timber, iron was sometimes used in limited areas, iron performed better than timber for tension members and iron was sometimes used for connecting the timber members.
Arch bridges are subdivided in a variety of configurations, depending on the material type used in construction.
Stone, concrete, or metal are the three most common materials, although timber may be used as well. Arch bridges are described in two arrangements: Deck arches, with the arch below the roadway, and through arches, with the arch rising above the roadway for at least a portion of the span.
Most arch bridges function by thrusting the forces at an angle into the side of the abutments or piers at each end of the spans. As such, they often have angled bearings called skewbacks. In these cases, the bridge can rest on its piers or abutments like a beam bridge, with a horizontal bearing sending forces vertically into the substructure.
Open Spandrel Arch: A type of deck arch bridge, as shown above, uses vertical columns to connect the deck to the arch. Closed Spandrel Arch: A type of deck arch bridge which uses solid concrete walls to connect the deck to the arch. Through Rainbow Arch: For concrete arch bridges, when the arch is above the roadway, it is often known as a rainbow arch.
Stone arch bridges are almost always deck arches, and closed spandrel in configuration. Engineers may categorize stone arch bridges based on the shape of the arch semicircular, segmental, or elliptical. Steel arch bridges, like concrete arch bridges, can be arranged as deck arch bridges or through arch bridges. Steel arch bridges are further categorized based on the design of the arch rib, the presence of hinges, and any bracing.
Deck arch bridges sometimes include diagonal bracing in addition to the vertical columns. In these cases, the bridge is known as a spandrel-braced arch bridge. A bridge can have hinges at the skewbacks bearings only a two-hinged arch bridge. A steel arch bridge can also have a third hinge at the crown mid-span , making it a three-hinged arch bridge. A suspension bridge consists of a deck that is held underneath main cables that are stretched out over the span from tall towers that rise above the deck.
Bridges is acting as cantilevered from the supports bear loads of the mid-span. Mainly there are two abutments at the mid-span of the bridge and then the bridge is cantilevered from these piers.
There may be several piers of this nature depending on the total length of the bridge. These bridges are constructed from structural steel and sections such as universal beam sections, H sections, rectangular hollow sections, circular hollow sections, etc are widely used as the members of the bridge.
The above figure indicates a typical cantilever bridge. There are different architecture have different appearance while maintaining the functional and structural requirements. Further, it is comparatively easy to construct these types of bridges than the other types of bridges as we can continue construction from one abutment toward the mid-span.
Once both sides are completed, the suspended span can be placed by connecting both the cantilevers. In addition, when there are requirements for headroom for the movements across the bridge, these types of bridges are more useful as the nature of this bridge provides it.
Suspension bridges are also called cable-stayed bridges are types of bridges constructed to support large spans. The cable running on top of the bridge connecting all the components of the bridge and anchored at the ends is the main cable. It is the element that carries loads of the bridge to the supporting structures and it can be identified as the key elements of the bridge.
It is a combination of steel wires and there are thousands of wires in the main cable. Suspender cables are also made from the same material. It is also a combination of steel wires. However, these cables are not that thick as the main cable. The deck is the area where the movement of people or vehicles are allowed. Trusses and bracings connected between trusses for the stability of the deck are hanging on the main cable by suspender cables.
The tower is the main component that supports the suspension cable. The key span of the bridge is maintained between the towers. Mostly the towers are made of concrete or steel and it is the tallest part of the bridge. The tensile force on the cable is supported by the anchor block rest on the ground which may be founded on a pile foundation.
One of the oldest types of bridges can be identified as arch bridges. There are different types of bridges fallen into this category. The load from the structure and the other applied loads are transferred to the abutment through the arching action.
There are different types of bridges constructed from different materials. When it starts to construct the arch bridges, there was no concrete. Therefore, different techniques are used in construction. Masonry arches, rock arches, etc are constructed in a stable manner to support the superstructure of the bridge.
These types of bridge foundation are used where the allowable bearing capacity of the soil is low and the bed of watercourse contains soft clay and silt. It favors foundations where hard soil is not found within reasonable depth 1.
Pile foundation is used in conditions where there is very soft soil and hard strata are not available at a reasonable depth. It is also used where scouring of a river as to be done and a large concentrated load is to be taken by the foundation. Well foundation of bridge is used when the bed has sandy soil and hard soil is available at m below the level of the watercourse.
Best suited on soil a condition having soft soils and sandy soils and heavy scouring is expected due to the large velocity of approach of the river.
Caisson foundation is a types of bridge foundation that is used where there is a hard stratum near the river bed and there is excessive water depth that is not economically sound to remove the water to enable sinking wells for well foundation. There are different types of bridges based on the structure how it distributes the load , the usage of the bridge, and the material used to make it.
This enables the bridges to serve various roles in various conditions without failure. The structure of a bridge dictates how the internal forces are distributed. The internal forces that act on a bridge are tension, compression, torsion, bending, and shear forces. The structure of a bridge will enable it to handle a specific type of force more and this is attributed to the notable structural members of a bride.
Based on this criterion, the following bridge types exist;. The main structural component of this bridge is the arch, usually located below the bridge. These types of bridges can only be fixed. The arch can be made of masonry stone, concrete, structural steel, cast iron, or even timber. Beam bridges are the simplest because they use horizontal beams. The beams can either span the area between abutments or transfer the forces to structural piers.
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