The bridge is a structure that is used in carrying a road, path, railway, etc. across a river, road, or another obstacle.
- Arch Bridges
- Beam Bridges
- Truss Bridges
- Cantilever Bridges
- Tied Arch Bridges
- Suspension Bridges
- Cable-Stayed Bridges
- Moveable Bridges
The arch is used as a main structural component which is always located below the bridge, never above it. With the help of mid-span piers, they can be built with more arches, depending on the kind of load and stress forces they must solve. The core part of the bridge is its abutments and pillars, which have to be constructed strong because they will take the weight of the whole bridge structure and forces.
Arch bridges can only be fixed, but they can be supported by any decking fiction, including transport of pedestrians, light or heavy rail, vehicles and even be used as water-carrying aqueducts. The most famous materials for the construction of arch bridges are masonry stone, concrete, timber, iron, cast iron, and structural steel.
2. Beam bridges:
Beam bridges are the simplest of forms one or several horizontal beams that can either simply span the area between abutments or relieve some of the pressure on structural piers. The core force that impacts beam bridges is the transformation of vertical force into shear and flexural load that is transferred to the support structures (abutments or mid-bridge piers), because of their simplicity, they were the oldest bridges known to man. Initially built by simply dropping wooden logs over short rivers or ditches, this type of bridge started being used extensively with the arrival of metalworks, steel boxes, and pre-stressed construction concrete. Beam bridges are separated into girder bridges, plate girder bridges, box girder bridges, and simple beam bridges.
Individual decking of the segmented beam bridge can be of the same length, variable lengths, inclined or V-shaped. The most famous example of a beam bridge is Lake Pontchartrain Causeway in southern Louisiana that is 23.83 miles (38.35 km) long.
3. Truss bridges:
It is a popular bridge design that utilized a diagonal mesh of most often triangle-shaped posts above the bridge to distribute forces across almost entire bridge structure. Individual elements of this structure (usually straight beams) can endure dynamic forces of tension and compression, but by distributing those loads across the entire structure, a whole bridge can handle many powerful forces and heavier loads than other types of bridges.
The 2 most common truss designs are the king posts are two diagonal posts handled by a single vertical post in the centre and queen posts are two diagonal posts, two vertical posts and horizontal posts that connect two vertical posts at the top.
The cantilever bridge is similar in appearance to arch bridges, but they support their load, not through a vertical of support but trough a diagonal of support with horizontal beams that are being supported only on one end. The vast majority of cantilever bridges use one pair of continuous spans that are placed between two piers, with beams meeting on the center over the obstacle that bridge spans (river, uneven terrain, or others). Cantilever bridge can be used in mid-bridge pears are their foundation from which they full extent in both directions toward other piers and abutments.
The size and weight capacity of the cantilever bridge impact the number of segments it uses. Simple pedestrian crossings over very short distances can use simple cantilever beam, but larger distances can use either two beams coming out of both abutments or multiple centre piers. Cantilever bridges cannot span very large distances. They can be bare or use truss formation both below and above the bridge, and most popular constriction material are structural steel, iron, and prestressed concrete.
5.Tied Arch Bridges:
Tied arch bridges are the same in design to arch bridges, but they transfer the weight of the bridge and load to the top chord that is contacted to the bottom cords in bridge foundation. The bottom tying cord can be reinforced decking itself or a separate deck-independent structure that interfaces with tie-rods.
They are often called bowstring arches or bowstring bridges and can be created in several variations, including shouldered tied-arch, multi-span discrete tied-arches, multi-span continuous tied-arches, single tied-arch per span and others. However, there is a precise differentiation between tied-arch bridges and bowstring arch bridges – the latter use diagonally shaped members who create a structure that transfers forces similar to in truss bridges.
Tied arch bridges can be visually very stunning, but they bring with them costly maintenance and repair.
Suspension bridges use spreading ropes or cables from the vertical suspenders to capture the weight of bridge deck and traffic, which is able to suspend decking over large spans, this type of bridge is very popular all around the world.
Originally made even in ancient times with materials such as ropes or vines, with decking’s of wood planks or bamboo, the modern variants use a wide array of materials. Because only abutments and piers (one or more) are fixed to the ground, the majority of the bridge structure can be very flexible and can often dramatically respond to the forces of wind, earthquake or even vibration of on-foot or vehicle traffic.
It uses deck cables that are directly joined to one or more vertical columns called towers or pylons, that can be put together near abutments or in the middle of the span of the bridge structure. Cables are used to connect columns in two ways – harp design i.e each cable is attached to the different points of the column, creating the harp-like strings and fan are designed to (all cables are connected to one point at the top of the column). This is a very different type of cable-driven suspension than in suspension bridges, where decking is held with vertical suspenders that go up to main support cable.
The majority of all bridges in the world are fixed in place, without moving parts that force them to remain in the same place until they are knocked down or fall down due to not anticipated stress or disrepair. However, some spaces are in need of multi-purpose bridges which can have movable parts or can be completely moved from one place to another. Even though these bridges are rarely seen, they serve an important function that makes them highly desirable.
(Note: For well explained types of canals : Click here )