A bridge is a structure that connects one place to another. There are many different types of bridges that are used today. For example, a beam bridge, a movable bridge, and arch bridge, and many more. The bridge that our team has chosen to focus on is the arch bridge. They are very rigid and have been in use for over 3000 years. They are one of the most popular types of bridges and are very prominent. An arch bridge is an elegant semi-circular structure. Even though some arch bridges might look different, the basic structure does not change. The meaning of an arch in architecture and civil engineering is curved structure or component that is used to span or cover an opening and to support loads from above. The arch was formed from the revolution of the vault. A fun fact is that due to the strength of the arch bridges, the bridges that the Romans built are still standing today!
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There are different types of arch bridges. The corbel arch bridge does not work like a normal arch bridge because they do not distribute the load and force across the bridge. They might look the same, but are built differently. They are made by layering stone or masonry. Also, they each have large cavaliers. Another type of bridge is the aqueduct or viaducts. The ancient Romans built them to connect long distances. It is a series of arch bridge that consisted of several layers. They reach very high unlike most arch bridges. A commonly seen bridge is the deck arch bridge. This is when the deck is on top of the arch rather than under. The through arch bridge is the opposite; the deck is under the arch rather than over. The tied arch bridge is also known as the bowstring bridge. It uses a tie between the two opposite ends of the bridge.
Arch bridges distribute the different forces through the entire bridge. As it has a curve design, it does not push the load straight down, but rather the load is conveyed along the curve of the arch. So essentially, it diverts the weight onto it’s two abutments. Abutments are the parts of the bridge that directly take the pressure. The from the deck puts pressure that's distributed to the abutments. The ground around the abutments is squeezed and pushes back on the abutments; for every action there is an opposite and equal reaction. The ground pushing back on the abutments vs the force being put on the abutments. This creates resistance. The resistance is passed from stone to stone till it is eventually pushing on the keystone which is supporting the load.
There are many different forces that act on a bridge. Tension, one of the forces, acting on an arch bridge is neglectable. This is because the curve has the ability to dissipate force outwards which reduces the tension on the underside of the arch. However, like every other bridge, the arch cannot “withstand physics forever”. The bigger the degree of the curvature (the larger the semicircle of the arch), the more tension on the underside of the bridge. If one was to build a big enough arch, the tension would overtake the strength of the bridge. So, instead of pushing down like most bridges, the load is carried along the arch (outwards). Another force on the bridge is compression.The bridge is always under compression. The force of compression is pushed outwards.
There are many different forces that act on a bridge. Tension, one of the forces, acting on an arch bridge is neglectable. This is because the curve has the ability to dissipate force outwards which reduces the tension on the underside of the arch. However, like every other bridge, the arch cannot “withstand physics forever”. The bigger the degree of the curvature (the larger the semicircle of the arch), the more tension on the underside of the bridge. If one was to build a big enough arch, the tension would overtake the strength of the bridge. So, instead of pushing down like most bridges, the load is carried along the arch (outwards). Another force on the bridge is compression.The bridge is always under compression. The force of compression is pushed outwards.
The hard part about building a bridge is that it does not have structural integrity until it meets in the middle. The key stone is the most important part of the bridge because that is what holds the arch together. The frame is built before the actual arch is built. This allows the stones to be in the right place while building. The frame is taken off after the stone is in position. However, arches do have the greatest natural strength. They were originally built of stone but are now built with modern materials, such as reinforced concrete or steel, to make it that much stronger.The ground around the abutments is squeezed and pushes back on the abutments.
If a series of wedge-shaped pieces are set side to side, it is an arch. These wedged pieces are called voussoirs. Each voussoir must be precisely cut so that it presses firmly against the surface of neighbouring blocks to carry the load above. The stone or piece at the center and top voussoir is called the keystone.The stone or piece at the center and top voussoir is called the keystone. Where the two vertical sides of the arch rises, into the curved arch it becomes, is known as the spring or springing line. During construction of an arch, there is a form of temporary wooden centring that supports the voussoirs until the keystone is placed. The curve of an arch can be semicircular, segmental (consisting of less than a half of a circle), or pointed (two intersecting arcs of a circle). Arches have great advantages over horizontal beams and can support more. This great capacity comes from the pressure downward on an arch that has the effect of forcing the voussoirs together instead of apart.
The pressure downward tend to squeeze the blocks outward radially, loads divert these outward forces downward to exert a diagonal force, called thrust, that will cause the arch to collapse if it is not properly buttressed. The vertical supports which an arch rests on must be large enough to buttress the thrust and direct it into the foundation (as in Roman triumphal arches). Arches can rest on very light supports when they occur in a row, because the thrust of one arch counteracts the thrust of its neighbours, and the system remains stable as long as the arches at either end of the row are buttressed. The horizontal thrust against the supports is small, this thrust can be further reduced by stretching a tie between the ends of the arch.
The pressure downward tend to squeeze the blocks outward radially, loads divert these outward forces downward to exert a diagonal force, called thrust, that will cause the arch to collapse if it is not properly buttressed. The vertical supports which an arch rests on must be large enough to buttress the thrust and direct it into the foundation (as in Roman triumphal arches). Arches can rest on very light supports when they occur in a row, because the thrust of one arch counteracts the thrust of its neighbours, and the system remains stable as long as the arches at either end of the row are buttressed. The horizontal thrust against the supports is small, this thrust can be further reduced by stretching a tie between the ends of the arch.
This system is used in such structures as arched stone bridges and ancient Roman aqueducts. The Romans used the semicircular arches in bridges, aqueducts, and large monumental architecture, they did not use mortar, relying simply on the precision of their stone dressing. Arches were known in ancient Egypt and Greece but were not suitable for monumental architecture. The Arabs popularized the pointed arch, and it was in their mosques that this form first acquired its religious connotations. Medieval Europe used the pointed arch, which composed a simple element in Gothic architecture. The segmental arch was introduced in the late Middle Ages, this form and the elliptical arch were a great use in bridge engineering because they permitted mutual support by a row of arches.These modern arches of steel, concrete, or laminated wood are highly rigid and lightweight.