Birdge_Notes


 * BRIDGE **

A bridge is a structure designed to save natural obstacles such asrivers, valleys, lakes or stretches of water, and artificial barriers such as railways or roads, in order to unite travelers roads, animals and goods.

Tipe of Bridges:

1. **Beam bridge****:** This is the earliest and simplest kind of bridge: a fallen tree lying over a stream. Is basically a horizontal structure that is resting on two piers, one at each side. Its weight and any traffic on it is directly supported by the piers. The weight is traveling directly downward. The compression force manifests itself on the top side of the beam bridge's deck (or roadway). This causes the upper portion of the deck to shorten. The result of the compression on the upper portion of the deck causes tension in the lower portion of the deck. This tension causes the lower portion of the beam to lengthen.



2. **Arch bridge****:** It is a semicircular structure with abutments on each end. The design of the arch naturally diverts the weight from the bridge deck to the abutments, and they're always under compression. The force of compression is pushed along the curve of the arch toward the abutments, practicly there's no tension because the natural curve of the arch and its ability to dissipate the force greatly reduces the tension on the underside of the arch. The greater the degree of curvature (the larger the semicircle of the arch), however, the greater the effects of tension on the underside.



3. **Suspension bridge****:** Its one where cables (or ropes, or chains) are strung across the obstacle and the deck is suspended from these cables. Modern suspension bridges have two towers through which the cables are strung. Thus, the towers are supporting the majority of the roadway's weight. The compression pushes down on the suspension bridge's deck, but because it is a suspended roadway, the cables transfer the compression to the towers, which dissipate the compression directly into the earth where they are entrenched.

The supporting cables, running between the anchorages are the recipients of the tension. The cables are literally stretched from the weight of the bridge and its traffic as they run from anchorage to anchorage. The anchorages are under tension too, but since they, like the towers, are held firmly to the earth, the tension they experience is dissipated.




 * Why were the bridges built? **



Human beings have used new technology to solve problems and ease their physical burdens, and bridges are technological tools that aim to solve the problem of crossing an obstacle in such a way as to shortening the effort and time needed to do so.


 * Did they provide benefits? To whom? Why? **



Some of the benefits of bridges are obvious: supplies of food and traded goods can get across an obstacle or through difficult terrain in a shorter time. In economic terms, the cost of travel and the financial benefits of increased social cohesion and sharing resources rise. Today bridges allow easy travel across major rivers and estuaries, over the new obstacles of motorways and railway lines, and between neighbouring islands. International trade and travel depend on shipping and air routes, but efficient distribution networks depend on bridges.


 * What are they made of? **


 * Wooden bridges, are quick to build and cost, but they are very resistant and durable, they are very sensitive to the weather.


 * Stone bridges, are extremely resistant, compact and durable, butnow construction is very expensive. Care necessary for their maintenance are scarce, as well resist climate agents.


 * <span style="color: #d3129b; font-family: 'Comic Sans MS',cursive; font-size: 110%;">Metal bridges: they are very versatile designs allow for large areas,are built quickly, but are expensive to build and are also subject to corrosion, both from the weather as the gases and smoke from factories and cities, which is an expensive maintenance.




 * <span style="color: #d3129b; font-family: 'Comic Sans MS',cursive; font-size: 110%;">Reinforced concrete bridges, are mounting rapidly, and in manycases supporting prefabricated elements, are resistant to breakinglonger spans the bridges of stone, although lower than those of iron, and maintenance costs are very low, since are very resistant to theaction of atmospheric agents




 * <span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 120%;">BRIDGES ALL OVER THE WORLD: **



**<span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%;">Golden Gate Bridge, San Francisco ** <span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%;">It is a famous bridge located in California, United States, whichconnects San Francisco peninsula to the north and south of Marin. The Golden Gate is the most famous bridge in San Franciscothough not the largest in this city, as the Bay Bridge is the main road. Its length is approximately one mile, is suspended from two towersof 745 feet. It has six lane for cars and a protected path forpedestrians and bicycles.



**<span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%;">Brooklyn Bridge, New York ** <span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%;">Its length is 6016 feet across the river east, and connecting theBrooklyn and Manhattan Island. The Brooklyn Bridge was the first suspension bridge in the world. Construction began in 1869 and was completed fourteen yearslater, The architectural style is Gothic and was a structure six timesstronger than what was needed and because it is still operatingwhen many others built around the same time have collapsed or been replaced. <span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; line-height: normal;">**Tower Bridge,** **London** <span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; line-height: normal;">Cross the River Thames in London and was the only movable bridge over the river when completed in 1894. The Tower Bridge is one of the best-known landmarks in London.This Victorian Bridge is now over 100 years. The center of the bridge can be raised to allow large ships of the sea pass Tower Bridge. I used to be raised about 50 times per day, but today standsonly 4 to 5 times a week **<span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%;">Sydney Harbour Bridge ** <span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%;">It is located on Sydney Harbour and connects the financial center ofSydney (Central Business District) to the north coast of the city,mostly residential and commercial. It was completed in 1932, after 8years of construction. Its beautiful arch is a metal structure that used for more than 6million rivets and a little over 53 tons of steel. <span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%; line-height: normal;">**Sydney Harbour Bridge** It is Located on Sydney Harbour and connects the financial center ofSydney (Central Business District) to the north coast of the city,Mostly residential and commercial. It Was completed in 1932, after8 years of construction. Its beautiful metal arch structure is to More Than That Used for 6million rivets and a little over 53 tons of steel.



**<span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%;">Great Belt East Bridge, Denmark ** <span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%;">In the summer of 1998 opened the bridge is for cars and trainsacross the sea Korsor (Sealand) and Nyborg (Funen). Passing through the bridge / tunnel, 11 miles long you have to paytoll. At 4 miles from the bridge east, about 1.6 miles take the form ofsuspension bridge (also known as the bridge Storebelt), whosecentral span of 5328 feet of light is the second largest in the world,and the two batteries from the Bridge This is the highest points inDenmark.

**<span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%;">San Diego-Coronado Bridge ** <span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%;">It is a concrete and steel structure that crosses the San Diego Bayto connect San Diego to Coronado. It is a bridge designed exclusively for car traffic was discontinuedcompletely the way for bicycles or walkers and many suicides occurred.

**<span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%;">Firth of Forth Bridge, Scotland ** <span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%;">The small town of South Queensferry is dominated by an imposingbridge whose length is 1 mile across the River Forth at SouthQueensferry linking the town of Inverkeithing. This spectacular railway bridge, the first of its kind in the world, was inaugurated in 1890 and is still considered one of the greatestengineering achievements of the Victorian era. This bridge was the one that inspired the Scottish writer Iain Banksfor his book entitled "The Bridge" (1986). **<span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%; line-height: normal;">Aquifer Bridge Magdeburg, Germany. ** <span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%; line-height: normal;">Built to link the Helba-Havel canal and the Mittelland, Germany, is anamazing bridge over flowing water and whose function is that theboats crossing the river Elbe from one extreme to another. Of 918meters long, it took 6 years to put it into operation, from 1997 to 2003 and it took about 500 million euros. <span style="color: #1eb4c8; font-family: 'Comic Sans MS',cursive; font-size: 110%; line-height: normal;">**Millau Bridge** Built in Aveyron, France, is the highest in the world. It was opened in 2004 after 36 months of hard work. Rose no less than 343 metersabove the river Tarn and has a route length of 2,460 meters linkingthe Causse du Larzac and Causse Rouge. Seven concrete pillarssustain all this colossal structure. They say it is like flying cross.