Parts of a bridge

In its technical aspect, the engineering of a traditional bridge differentiates, in addition to the foundations, two essential parts: the superstructure and the infrastructure, and in them, the following basic components can be broken down:

Regarding the architectural structure, in a bridge you can distinguish:

Analysis and design

Unlike buildings, whose design is directed by architects, bridges are usually designed by engineers. This is due to the importance of the engineering requirements, that is, clearing the obstacle and having the necessary durability to endure, with minimal maintenance, in an aggressive outdoor environment.[9]​ Bridges are analyzed first; The distributions of the bending moment and the shear force due to the applied loads are calculated. For this, the finite element method is the most popular. The analysis can be one-dimensional, two-dimensional or three-dimensional. For most bridges, a two-dimensional plate model (often with reinforcing beams) or a bottom-up finite element model is sufficient.[10] Once the analysis is completed, the bridge is designed to resist the applied bending moments and shear forces, and section sizes with sufficient capacity to withstand the stresses are selected. Many bridges are built with prestressed concrete, which has good durability properties, either by prestressing the beams before installation or post-tensioning in situ.

In most countries, bridges, like other structures, are designed according to the principles of Load and Resistance Factor Design (LRFD). In simple terms, this means that the load is factored by a factor greater than unity, while the strength or capacity of the structure is multiplied by a factor less than unity. The effect of the factored load (stress, bending moment) must be less than the factored resistance to that effect. Both factors take into account uncertainty and are greater when it is greater.

Efficiency

The structural efficiency of a bridge can be considered as the ratio (quotient) between the load that the bridge can support and the weight of the bridge itself, given a certain set of materials. In a common challenge, some students are divided into groups and given a certain number of wooden sticks, a building distance, and glue, and then asked to build a bridge that will be tested to destruction by progressively adding load to its center. The bridge that resists the greatest load is the most efficient. A more formal measurement of this exercise is to weigh the completed bridge rather than measure a fixed quantity of provided materials and determine the multiple of this weight that the bridge can support, a test that emphasizes the economy of materials and the efficiency of glued assemblies.

The economic efficiency of a bridge depends on its location, the potential traffic it can handle, and the amount of savings involved in building the bridge (instead of, for example, a ferry, or a longer route) compared to its cost. Its useful life cost is made up of materials, labor, machinery, engineering, cost of money, insurance, maintenance, renovation and, finally, demolition and disposal of its associated, recycling and replacement, less the scrap value and reuse of its components. Bridges that employ compression only are relatively inefficient structurally, but can be highly efficient economically where the necessary materials are available close to their location and the cost of labor is low. For medium-sized bridges, braced or girder bridges are usually the most economical, while in some cases the appearance of the bridge may be more important than its cost efficiency. Larger bridges generally must be built suspended.

Aesthetics

Most bridges have a utilitarian appearance, but in some cases, the appearance of the bridge can be of great importance.[12] This is often the case with a large bridge that serves as the entrance to a city, or that crosses over the main entrance to a port. They are sometimes known as landmark bridges. Designers of bridges in parks and along greenways also tend to place more importance on aesthetics. Some examples are the stone bridges of the Taconic State Parkway in New York.

To create a beautiful image, some bridges are built much higher than necessary. This type, often found in oriental-style gardens, is called Moon Bridge, which evokes a crescent full moon. Other garden bridges may cross only a dry bed of stream-washed pebbles, with the sole intention of conveying the impression of a stream. Often in palaces, a bridge is built over an artificial waterway as a symbol of passage to an important place or state of mind. A set of five bridges crosses a winding waterway in an important courtyard of the Forbidden City in Beijing, China. The central bridge was reserved exclusively for the use of the Emperor and Empress, with their attendants.

Existen cinco tipos principales de puentes: puentes viga, en ménsula, en arco, colgantes y atirantados. El resto son derivados de estos.

For its use

A bridge is designed for railways, automobile or pedestrian traffic, gas or water pipelines, or for maritime traffic. In some cases there may be restrictions on its use. For example, it may be a bridge on a highway and be prohibited for pedestrians and bicycles, or a pedestrian bridge, possibly also for bicycles.

The undersides of bridges around the world are frequent spots for graffiti.

An aqueduct is a bridge that transports water. Similar to a viaduct, it connects points of similar height.

Structural and evolutionary taxonomy

Bridges can be classified by the way in which the four forces of tension, compression, bending, and shear stress are distributed throughout their structure. Most bridges employ all of the major forces to some degree, but only a few predominate. The separation of forces can be quite clear. In a suspension bridge, the elements in tension are different in shape and arrangement. In other cases the forces may be distributed among a large number of members, such as in a braced one, or not very perceptible to the naked eye, as in a box of beams. Bridges can also be classified by their lineage.

Decorative and ceremonial bridges

To create a beautiful image, some bridges are built much higher than necessary. This type, frequently found in East Asian-style gardens, is called "moon bridge", evoking the rising full moon.

Other garden bridges may cross only a dry stream of washed pebbles, attempting only to convey the feeling of a real stream.

Commonly in palaces a bridge will be built over an artificial stream of water symbolically as a passage to an important place or state of mind. A set of five bridges cross a winding stream in an important garden in the Forbidden City in Beijing, China. The central bridge was reserved exclusively for the use of the emperor, the empress and their servants.

Movable bridges

Below are some of the mobile bridge constructions:.

Bridge failures

In a statistic carried out in 1976, on the causes of failure or breakage of 143 bridges around the world, it turned out:

This shows that hydraulic aspects are fundamental in bridges; A good knowledge of these aspects will make the bridge safer and cheaper.[13]​.

Bridge condition monitoring

There are several methods to monitor the condition of large structures such as bridges. Today, many large-span bridges are routinely monitored with an array of sensors. Many types of sensors are used, such as strain transducers, accelerometers,[14] inclinometers) and GPS. Accelerometers have the advantage of being inertial, that is, they do not need a reference point to measure. This is often a problem for measuring distances or deviations, especially if the bridge is over water.

One option for structural integrity monitoring is “non-contact monitoring,” which uses the Doppler effect (Doppler shift). A laser beam from a laser Doppler vibrometer is directed at the point of interest, and the amplitude and frequency of the vibration are extracted from the Doppler shift of the laser beam frequency due to the motion of the surface.[15]​ The advantage of this method is that the setup time of the equipment is faster and, unlike an accelerometer, this allows measurements to be made on multiple structures in the shortest time possible. Additionally, this method can measure specific points on a bridge that may be difficult to access. However, vibrometers are relatively expensive and have the disadvantage that a reference point is needed to measure.

To aid bridge inspection, snapshots in time of a bridge's external state can be recorded using lidar,[16]​ which can provide measurements of bridge geometry (to facilitate construction of a computer model), but the accuracy is often insufficient to measure bridge deflections under load.

While larger modern bridges are routinely monitored electronically, smaller bridges are typically inspected visually by trained inspectors. There is great research interest in the challenge posed by smaller bridges, as they are often located in remote locations and do not have on-site electrical power. Possible solutions are installing sensors on a specialized inspection vehicle and using their measurements as it passes over the bridge to infer information about the state of the bridge.[17]​[18]​[19]​ These vehicles can be equipped with accelerometers, gyrometers, laser Doppler vibrometers[20]​[21]​ and some even have the ability to apply a resonant force to the road surface to dynamically excite the bridge at its resonant frequency.

Algunos puentes pueden tener instalaciones especiales, como la torre del puente Nový Most en Bratislava, que contiene un restaurante. En otros puentes suspendidos, pueden instalarse antenas de transmisión. Un puente sobre el Arno en Florencia (Italia) tiene tiendas comerciales a ambos lados.

Un puente puede contener líneas eléctricas, como el puente Storstrøm. Además los puentes también soportan tuberías, líneas de distribución de energía o de agua mediante una carretera o una línea férrea.

Materials

Various materials are used in the construction of bridges. In ancient times, wood was mainly used and later stone. More recently, metal bridges have been built, a material that gives them much greater strength. The main materials used for the construction of bridges are:

Parts of a bridge

In its technical aspect, the engineering of a traditional bridge differentiates, in addition to the foundations, two essential parts: the superstructure and the infrastructure, and in them, the following basic components can be broken down:

Regarding the architectural structure, in a bridge you can distinguish:

Analysis and design

Unlike buildings, whose design is directed by architects, bridges are usually designed by engineers. This is due to the importance of the engineering requirements, that is, clearing the obstacle and having the necessary durability to endure, with minimal maintenance, in an aggressive outdoor environment.[9]​ Bridges are analyzed first; The distributions of the bending moment and the shear force due to the applied loads are calculated. For this, the finite element method is the most popular. The analysis can be one-dimensional, two-dimensional or three-dimensional. For most bridges, a two-dimensional plate model (often with reinforcing beams) or a bottom-up finite element model is sufficient.[10] Once the analysis is completed, the bridge is designed to resist the applied bending moments and shear forces, and section sizes with sufficient capacity to withstand the stresses are selected. Many bridges are built with prestressed concrete, which has good durability properties, either by prestressing the beams before installation or post-tensioning in situ.

In most countries, bridges, like other structures, are designed according to the principles of Load and Resistance Factor Design (LRFD). In simple terms, this means that the load is factored by a factor greater than unity, while the strength or capacity of the structure is multiplied by a factor less than unity. The effect of the factored load (stress, bending moment) must be less than the factored resistance to that effect. Both factors take into account uncertainty and are greater when it is greater.

Efficiency

The structural efficiency of a bridge can be considered as the ratio (quotient) between the load that the bridge can support and the weight of the bridge itself, given a certain set of materials. In a common challenge, some students are divided into groups and given a certain number of wooden sticks, a building distance, and glue, and then asked to build a bridge that will be tested to destruction by progressively adding load to its center. The bridge that resists the greatest load is the most efficient. A more formal measurement of this exercise is to weigh the completed bridge rather than measure a fixed quantity of provided materials and determine the multiple of this weight that the bridge can support, a test that emphasizes the economy of materials and the efficiency of glued assemblies.

The economic efficiency of a bridge depends on its location, the potential traffic it can handle, and the amount of savings involved in building the bridge (instead of, for example, a ferry, or a longer route) compared to its cost. Its useful life cost is made up of materials, labor, machinery, engineering, cost of money, insurance, maintenance, renovation and, finally, demolition and disposal of its associated, recycling and replacement, less the scrap value and reuse of its components. Bridges that employ compression only are relatively inefficient structurally, but can be highly efficient economically where the necessary materials are available close to their location and the cost of labor is low. For medium-sized bridges, braced or girder bridges are usually the most economical, while in some cases the appearance of the bridge may be more important than its cost efficiency. Larger bridges generally must be built suspended.

Aesthetics

Most bridges have a utilitarian appearance, but in some cases, the appearance of the bridge can be of great importance.[12] This is often the case with a large bridge that serves as the entrance to a city, or that crosses over the main entrance to a port. They are sometimes known as landmark bridges. Designers of bridges in parks and along greenways also tend to place more importance on aesthetics. Some examples are the stone bridges of the Taconic State Parkway in New York.

To create a beautiful image, some bridges are built much higher than necessary. This type, often found in oriental-style gardens, is called Moon Bridge, which evokes a crescent full moon. Other garden bridges may cross only a dry bed of stream-washed pebbles, with the sole intention of conveying the impression of a stream. Often in palaces, a bridge is built over an artificial waterway as a symbol of passage to an important place or state of mind. A set of five bridges crosses a winding waterway in an important courtyard of the Forbidden City in Beijing, China. The central bridge was reserved exclusively for the use of the Emperor and Empress, with their attendants.

Existen cinco tipos principales de puentes: puentes viga, en ménsula, en arco, colgantes y atirantados. El resto son derivados de estos.

For its use

A bridge is designed for railways, automobile or pedestrian traffic, gas or water pipelines, or for maritime traffic. In some cases there may be restrictions on its use. For example, it may be a bridge on a highway and be prohibited for pedestrians and bicycles, or a pedestrian bridge, possibly also for bicycles.

The undersides of bridges around the world are frequent spots for graffiti.

An aqueduct is a bridge that transports water. Similar to a viaduct, it connects points of similar height.

Structural and evolutionary taxonomy

Bridges can be classified by the way in which the four forces of tension, compression, bending, and shear stress are distributed throughout their structure. Most bridges employ all of the major forces to some degree, but only a few predominate. The separation of forces can be quite clear. In a suspension bridge, the elements in tension are different in shape and arrangement. In other cases the forces may be distributed among a large number of members, such as in a braced one, or not very perceptible to the naked eye, as in a box of beams. Bridges can also be classified by their lineage.

Decorative and ceremonial bridges

To create a beautiful image, some bridges are built much higher than necessary. This type, frequently found in East Asian-style gardens, is called "moon bridge", evoking the rising full moon.

Other garden bridges may cross only a dry stream of washed pebbles, attempting only to convey the feeling of a real stream.

Commonly in palaces a bridge will be built over an artificial stream of water symbolically as a passage to an important place or state of mind. A set of five bridges cross a winding stream in an important garden in the Forbidden City in Beijing, China. The central bridge was reserved exclusively for the use of the emperor, the empress and their servants.

Movable bridges

Below are some of the mobile bridge constructions:.

Bridge failures

In a statistic carried out in 1976, on the causes of failure or breakage of 143 bridges around the world, it turned out:

This shows that hydraulic aspects are fundamental in bridges; A good knowledge of these aspects will make the bridge safer and cheaper.[13]​.

Bridge condition monitoring

There are several methods to monitor the condition of large structures such as bridges. Today, many large-span bridges are routinely monitored with an array of sensors. Many types of sensors are used, such as strain transducers, accelerometers,[14] inclinometers) and GPS. Accelerometers have the advantage of being inertial, that is, they do not need a reference point to measure. This is often a problem for measuring distances or deviations, especially if the bridge is over water.

One option for structural integrity monitoring is “non-contact monitoring,” which uses the Doppler effect (Doppler shift). A laser beam from a laser Doppler vibrometer is directed at the point of interest, and the amplitude and frequency of the vibration are extracted from the Doppler shift of the laser beam frequency due to the motion of the surface.[15]​ The advantage of this method is that the setup time of the equipment is faster and, unlike an accelerometer, this allows measurements to be made on multiple structures in the shortest time possible. Additionally, this method can measure specific points on a bridge that may be difficult to access. However, vibrometers are relatively expensive and have the disadvantage that a reference point is needed to measure.

To aid bridge inspection, snapshots in time of a bridge's external state can be recorded using lidar,[16]​ which can provide measurements of bridge geometry (to facilitate construction of a computer model), but the accuracy is often insufficient to measure bridge deflections under load.

While larger modern bridges are routinely monitored electronically, smaller bridges are typically inspected visually by trained inspectors. There is great research interest in the challenge posed by smaller bridges, as they are often located in remote locations and do not have on-site electrical power. Possible solutions are installing sensors on a specialized inspection vehicle and using their measurements as it passes over the bridge to infer information about the state of the bridge.[17]​[18]​[19]​ These vehicles can be equipped with accelerometers, gyrometers, laser Doppler vibrometers[20]​[21]​ and some even have the ability to apply a resonant force to the road surface to dynamically excite the bridge at its resonant frequency.

Algunos puentes pueden tener instalaciones especiales, como la torre del puente Nový Most en Bratislava, que contiene un restaurante. En otros puentes suspendidos, pueden instalarse antenas de transmisión. Un puente sobre el Arno en Florencia (Italia) tiene tiendas comerciales a ambos lados.

Un puente puede contener líneas eléctricas, como el puente Storstrøm. Además los puentes también soportan tuberías, líneas de distribución de energía o de agua mediante una carretera o una línea férrea.

Materials

Various materials are used in the construction of bridges. In ancient times, wood was mainly used and later stone. More recently, metal bridges have been built, a material that gives them much greater strength. The main materials used for the construction of bridges are: