Arch Bridge is the bridge in which the horizontal thrust developed is restrained by the abutments provided at each end of the bridge. As the name itself implies, it is curve-shaped or arch-shaped.
It is one of the oldest forms of a bridge that has been used since ancient times. The reason behind the popularity of the arch bridge is that it not only provides structural support but is also aesthetically pleasing in nature.
During ancient times, it was constructed using stones and bricks but in recent days, it is constructed using ferroconcrete and steel.
a. It may be fixed, hinged or tied at the supports.
b. The curved shape of the arch bridge leads to the development of horizontal forces in addition to the vertical forces both in the fixed and the hinged arches.
c. In the case of fixed arches, the fixing moment is also developed at the supports.
d. The horizontal supports at the hinge develops sagging moment thereby reducing the cross-section of the arch.
e. In the case of two and three-hinged arches, there is no bending moment on the arch at the springing. In these types of arches, only the thrusts are transmitted to the abutments.
f. The forces and the moments both changes due to the rotation and displacement of the supports.
g. In the two hinged arches, the structure is affected by the displacement of the abutments but remains unaffected by the rotation of the abutments.
Types of Arch Bridge:
1. Deck Bridge:
~ It is the arch bridge that provides direct support to the traffic loads through a structure that is built on the top of the crown of the arch. Due to this reason, the arch of the deck bridge is considered as an ideal arch.
~ The area between deck and arch is known as a spandrel. When spandrel is solid(i.e. constructed using masonry or stone), it is called closed-spandrel deck arch bridge.
~ When the deck is supported by vertical columns rising from the arch then it is called open-spandrel deck arch bridge.
~ If the deck of the bridge is supported only at the top of the arch then it is called cathedral arch bridge.
Some of the examples are as follows:
a. Wanzhou Bridge/Wanxian Bridge: The Wanzhou bridge is a famous deck bridge located in Wanzhou, China. The span of this bridge is 864.12m ( 2, 835 feet).
b. New River Gorge Bridge: The New River Gorge Bridge is a famous deck bridge located in West Virginia, United States. The span of this bridge is 924m (3,030 feet).
2. Through Arch Bridge:
~ It is the bridge in which the upper deck is found at the spring line of the arch. It is also commonly referred to as the half-through arch bridge.
~ Its base is at or below the deck, but top rises above it.
~ Mostly, it is constructed using the reinforced concrete or steel as the construction materials.
~ The central part of this bridge is supported by the arch via suspension cables or tie bars and end parts are supported from below as in deck arch bridge.
Some of the famous examples can be listed as follows:
a. Sydney Harbour Bridge: The Sydney Harbour Bridge is a through bridge located in Sydney, Australia. The span of this bridge is 1,149m (3, 770 feet).
b. Hell Gate Bridge: The Hell Gate Bridge is a through bridge located in Sydney, Australia. The span of this bridge is 5,151m (16,900 feet).
3. Moment Tied Bridge:
It is the type of arch bridge in which the floor beams are connected to a tie to form an affiliation between the arch and the tie.
4. Pinned-Pinned Concrete Arch Bridge:
It is the arch bridge that consists of roller supports which permits the linear motion at the side of rotation.
5. Bowstring Arch Bridge:
~ It is also called Tied- Arch Bridge.
~ This bridge essentially consists of tension ties between two opposite ends of the arch. The tension ties are responsible for carrying the axial loads and the unsymmetrical flexure carried by arch.
6. Corbel Arch Bridge:
It is constructed by a sequential layer of masonry or stones with successive large cantilevers.
Advantages of Arch Bridge
a. Better Resistance:
It offers a better level of resistance to the imposed loads. It receives additional strength from the aciform design of the bridge and thus provides a higher degree of resistance to the bending forces and associated loads.
b. Higher Pressure Resistance:
It offers better resistance to the pressure due to the unique arch style of the bridge. It allows the load to be distributed thus ensuring that no part of the bridge is subjected to excessive pressure.
c. Many Choices of Construction Materials:
It offers great flexibility and options in terms of construction materials. This bridge can also be constructed using stones, bricks and other similar natural materials.
d. Sound Structure:
The structure of the arch bridge is relatively sound. The modern type of the arch bridge is constructed using lighter construction materials which sound even for long spans.
e. No Distortion:
The structure of the arch bridge mostly does not have any type of distortion. This is because the half-circle style or the arch form of bridge design ensures that no distortion occurs to the structure even when it is subjected to excessive pressure or weight.
It is strong enough and capable of withstanding the loads imposed efficiently.
g. Economic and Affordable:
It is a relatively economic type of bridge. It offers flexibility in terms of construction materials and thus cost-efficient locally available materials can be used.
Disadvantages of Arch Bridge
a. Limitation on Bridge Location:
It does not offer much flexibility in terms of the location. It can be constructed only in specific areas.
b. Limitation on Span:
This type of bridge does not offer much flexibility in terms of the span i.e. in arch bridges the span is restricted.
c. Need for Additional Maintenance:
The structure and design of the arch bridge are such that it requires frequent and additional maintenance.
d.Need for Additional Support:
In general, It requires some type of additional support on the sides.
e. Longer Construction Time:
The construction of the arch bridge requires a considerably longer time for completion.