Bridges have been built in different ways since the first humans. When we look at the history of bridges, the first humans used to pass themselves or their animals over an obstacle while crossing a brooklet. In time, small bridges that cross rivers and bridges that are engineering marvels connecting even continents passing over the seas were built. According to Guinness World Records, the oldest bridge is in Izmir, Turkey, on the Meles River. It is still in use now and is estimated to have been built in 1600 BC.
Bridges have constantly changed with the change of materials and technology. Here, the influence of geography on matters such as the supply of material can also be seen. Bridges have been produced with different types of materials such as rock, wood, reinforced concrete, metal and composite from past to present.
Bridges are often designed around the need to overcome a particular obstacle. After these structures are built, they are intended to serve people for years. It has to be designed very well and built in a quality way in order to successfully pass the factors such as weather conditions, earthquakes, excessive use, and provide service over the years. The correct type of bridge design should be made on the existing land. Here, construction techniques and the conditions of the land come into play.
7 Different Types of Bridges
- Arch Bridge
- Beam Bridge
- Cantilever Bridge
- Truss Bridge
- Suspension Bridge
- Cable-Stayed Bridge
- Tied-Arch Bridge
Arch bridges are basically under pressure only, so they can be constructed from building materials with less tensile strength, such as concrete and steel. You can also see examples made of brick, wood, aluminum and forged steel. An Arch Bridge works by transferring downward gravity pressure to the center of the structure, i.e. the interior. This principle that allows the arch to support the surface on it is called compression. The compression force created here supports the surface of the structure.
Stone Arch Bridge is an example of an arch bridge completed in the state of Minnesota in America in 1883.
Beam bridges are the oldest and cheapest among other types of bridges. The weight of the beam is pushed directly towards the piers. It consists of one or more beam systems. It has a horizontal bearing element supported at both ends. When we compared arch bridges with the same load and span in beam bridges, greater internal forces occur. The forces occurring here are due to the tendency of the beams to bend. Beams trying to bend create pressure in the upper parts of the structure and tensile stresses in the lower parts of the structure.
We use wood, reinforced concrete, prestressed concrete or steel as material for the beams. In beam bridges, there are three types of systems with plate-web, trussed, or box sections. In the construction of long girder bridges, truss system beam bridge design is generally applied.
One of the most striking examples of girder bridges is the Magdeburg Water Bridge: It is a large aqueduct bridge located near Magdeburg, in the center of Germany.
In cantilever bridges, the support is made from a single point. There are two types of consoles, single arm and double arm. Most of the cantilever bridges have a suspended beam that extends horizontally to the arms extending in two directions. The load is generally supported from both above and below. These bridges can be made of reinforced concrete and steel.
The bridge with the longest cantilever span in the world is the Pont de Quebec bridge. It was opened in Canada in 1919. The bridge has 1801 feet (549m) cantilever span. The overall length of the bridge is 3238 feet (987 m).
The truss bridge is the main load-bearing of the superstructure. The load depends on small interconnected units. When this structure is formed, it looks like a jigsaw puzzle. When the bridge truss beams and bridge sizes are enlarged, the box-beam method is adopted. This is more applicable and effective. This ensemble of triangular structures is interconnected by welding or rivets. Vertical supports help the bridge to hold. Diagonal cage segments allow the load to move towards the center and it is desirable that the load be at the common point as much as possible. This situation causes compression and this is the operating system in which the bridge remains stable. When building a long span bridge, the height of the bridge is changed along the span direction. The aim is to create a curved truss. In the medium and small spans, the cage height called flat wire mesh is adopted.
5 Other Kinds of Truss Bridge Designs
- Baltimore truss bridge
- Long truss bridge
- Howe truss bridge
- Vierendeel truss bridge
- Warren truss bridge
Suspension bridges try to pull the load using cable. A flat deck is built for the flow of vehicle traffic. In suspension bridges, the tower carries the main cables. Anchors pull the cables outwards and downwards to keep the cable taut. In the stretching process, the holding element anchors are connected to a solid ground. There are steel and reinforced concrete examples of the towers. It is also seen that stone was used for the tower in old buildings. The deck is designed in a steel cage or box section. In projects where aerodynamic calculations are important and the effect of wind is high, box-section designs are made by considering aerodynamics.
The main carrier system consists of cables and chains. Since the cables and chains are constantly under the tensile force, they do not undergo buckling, so their rigidity is not important. Towers are completely under compression. The most important point in suspension bridges are decks. The rigidity of the bridge is related to the deck. Suspension bridges are built in areas such as the strait where there is a lot of wind flow. Therefore, aerodynamics is very important in suspension bridges to provide rigidity to the deck. We can give examples of these bridges such as Golden Gate Bridge, Akashi Kaikyo Bridge, Yavuz Sultan Selim Bridge.
A cable-stayed bridge is a suspension bridge that connects the cross beam or bridge deck directly to the pillars or towers. When we look at the work system of the cable-stayed bridge. It mirrors the suspension bridge and its work system. The point where it differs from a conventional suspension bridge is that suspension bridges have a main cable, but cable-stayed bridges do not have a main cable. There are many cables and these cables are fixed to the tower. The tension force that occurs here keeps the main deck stable.
Sutong Yangtze River Bridge is one of the famous examples that was built in china to connect Nantong and Changshu With a 1,088-meter (3,570 ft) span, Sutong Yangtze River Bridge became the longest main span in the world in 2008-2012. The bridge has two side spans, each with a span of 300 meters (980 ft). The bridge received the 2010 Outstanding Civil Engineering Achievement Award (OCEA) by the American Society of Civil Engineers.
Tied-arch bridges build using the characteristics of the arch bridge and suspension bridge. We use force from both horizontal sides to support an arched structure. However, some different approaches may be required in design phase. Instead of a system that supports the structure seen in arch bridges from below, the arch rises above the road. Top-down ties are used to increase the support of the ground. Springs are used to support the load and keep the bridge stable.
The Fremont Bridge is a steel arch bridge over the Willamette River in Portland, Oregon, USA. It is the second longest connected arch bridge in the world. Number one is the Caiyuanba Bridge over the Yangtze River, China. The bridge was designed by WSP USA company and built by Murphy Pacific Corporation.
As a result, when we look at bridges outside of architecture and engineering, they have the feature of connecting continents, societies, and many other things and providing excellent convenience. The development that has taken place here is a great achievement and luxury of humanity. When we go through a structure, it is necessary to look at it from a different perspective and to better read between lines.