If we take a look around our cities we can find that, without bridges there is no way that we could have expanded that much. Bridges helps to save distances and could also be an icon inside and out the city. Without a bridge, Caracas would not have its expansion to the south and southwest part: El ParaĆ­so, Bello Monte... all the mainly residential urbanizations would not exist. For that reason we are going to study bridges, beginning with the concept of a bridge, the benefits they produce, the different types of bridges and a little explanation of the commonly used materials.



In order to talk about bridges, first we need to now what it is. A Bridge is a technological tool that aim to solve the problem of crossing an obstacle. The better the bridge is, the less attention the user will need to pay it. For this characteristic, some benefits  of bridges are related to their function. Therefore bridges help to transport supplies of food in short time; reduce distances that improve the sharing of ideas and streghten international relationships.   


There are different types of bridges, among them are:  Beam Bridges, Cantilever Bridges, Arch Bridges, Suspention Bridges and the new ones: Cable Stay Bridges.  A Beam Bridge was the first bridge we found in nature. It is simple and it has two main elements: Beam and Pier. Usually this bridges are made of concrete, wood, stone and steel. The main disadvantage of this type of bridges are that they are not built to support shipping pass ( ships can not pass below them!) and also, they sag and hog causing them to crumple.  

              Beam Bridges have a lot of ways to look deep and dont weight too much specially this type of bridges; In the XIXth century people developed the "Truss", that it is a way to distribute the load of the bridge.  


The second type of bridge, the Cantilever Bridge is a modification of the Truss Bridge (Shown above) It main characteristic is that it has two main towers on the sides and no pier at the centre.



When we have a succesion of archs the bridge dissipates the loads easily. Arch Bridges are the most common bridges around the world and were very popular in the XIXth Europe. They are made of stone, iron, bronze, brass (aleation of cooper and zinc)... The disadvantage is that the piers need to be located on bedrock to support the loads. Note that the bigger the arch is, the weaker it becames!!   Nowadays arch bridges are made of steel bars within concrete, that make them ligther  






The fourth of the mentioned bridges is the Suspention Bridge, this one is a road deck suspended from cables that does not have a central pier. It uses two towers at the extreme of the bridge to stress the cables. This bridges are usually made of steel cables, iron links and concrete blocks. The anchorages must be over solid rock to support the load (just like arch bridges!). The disadvantage is that  it is unstable to fast winds and susceptible to resonance phenomena.





The newer of bridges are the Cable Stayed Bridges; that are a variation of the suspention bridge. The only difference is that it has a central pier or anchorage. The material nowaydays is plastic with a concrete tower.







As a side note we can say that a factor that affects the structure and appearance is the scale. It is important to find the balance between form and function. Also, bridges are important to people because they may be Icons inside and outside a city or town. So, why are bridges that important? It is mainly because they   facilitate the communication between cities, improving the transference of ideas, culture, producing diversity and heterogeneity.



As we can see there are a lot of bridges, all of them made of different materials and with its own disadvantages, beam bridges hogs and sag; arch bridges might be unstable if the arch is too big, cable stayed bridges and suspension bridges are susceptible to the resonance phenomena... But above all that bridges are a connection, a way to be related to other, no matter people or cities.


Sources: (Great page!) (So technical...) Images were taken from different web pages... all of them searched with google