Bridge+Project

media type="youtube" key="67QVfvQMtW4" height="315" width="420" **Bridges ** Bridges: ** A bridge ** is a link or connection between two objects, usually places either side of an obstacle, such as a river, chasm, or estuary. Bridges are technological tools that aim to solve the problem of crossing an obstacle in such a way as to cut down the effort and time needed to do so. The main types of bridges are: arches, beam bridges, cable-stayed bridges, cantilever bridges and suspension bridges. **Arch Bridges ** The essence of an arch is that ideally there should be no tendency for it to bend, except under live loads. The entire arch is in compression. The compression is transferred into the abutments, and ultimately resisted by tension in the ground under the arch. **Beam Bridges ** The design is as simple as a single rigid 'beam', resting on supports at either end and unsupported in the middle. The weight of the beam, and of any traffic on it, is carried directly to the ground by the supports, often called 'piers' in the trade. **Cable-Stayed Bridges **  **Cable-Stayed Bridges** consist of one or more columns (normally referred to as towers or pylons ), with cables supporting the bridge deck. The cables are in tension, and the deck is in compression. **Cantilever Bridges ** A cantilever bridge is a bridge built using cantilevers structures that project horizontally into space, supported on only one end.  As with the beam, the bending stresses and shear stresses vary throughout the structure. **Suspension Bridges ** A suspension bridge is a type of bridge in which the deck (the load-bearing portion) is hung below suspension cables on vertical suspenders. <span style="font-family: Arial,sans-serif;">The suspension cables must be anchored at each end of the bridge, since any load applied to the bridge is transformed into a tension in these main cables. **<span style="font-family: Arial,sans-serif;">Truss Bridges ** <span style="font-family: Arial,sans-serif;">A truss bridge is a bridge composed of connected elements (typically straight) which may be stressed from tension, compression, or sometimes both in response to dynamic loads. **<span style="font-family: Arial,sans-serif;">Golden Gate Bridge ** <span style="font-family: Arial,sans-serif;">The Golden Gate Bridge is located in San Francisco, California, in USA. The purpose of the bridge is a Motorway, freeway bridges. The type of bridge is a suspension bridge and the materials used are steel.
 * <span style="font-family: Arial,sans-serif;">The San Francisco`s Golden Gate **

<span style="font-family: Arial,sans-serif;">The technology involved in its construction: This Bridge has cables suspended between towers, plus vertical suspender cables that carry the weight of the deck below, upon which traffic crosses.

<span style="font-family: Arial,sans-serif;">The suspension cables are anchored at each end of the bridge, since any load applied to the bridge is transformed into a tension in these main cables. The main cables continue beyond the pillars to deck-level supports, and further continue to connections with anchors in the ground. The roadway is supported by vertical suspender cables or rods, called hangers.

<span style="font-family: Arial,sans-serif;">The New York’s Manhattan Bridge designer Leon Moisseiff produced the basic structural design of the Golden Gate Bridge, introducing his "deflection theory" by which a thin, flexible roadway would flex in the wind, greatly reducing stress by transmitting forces via suspension cables to the bridge towers.

<span style="font-family: Arial,sans-serif;">The designers: Joseph Strauss was chief engineer in charge of overall design and construction of the bridge project. However, because he had little understanding or experience with cable-suspension designs, responsibility for much of the engineering and architecture fell on other experts. Strauss' initial design proposal (two double cantilever spans linked by a central suspension segment) was unacceptable from a visual standpoint. The final graceful suspension design was conceived and championed by Leon Moisseiff.

<span style="font-family: Arial,sans-serif;"> Irving Morrow, a relatively unknown residential architect, designed the overall shape of the bridge towers, the lighting scheme, and Art Deco elements such as the streetlights, railing, and walkways. The famous Intenational Orange color was originally used as a sealant for the bridge.

<span style="font-family: Arial,sans-serif;">The advantages/disadvantages of the bridge for the specific community: <span style="font-family: Arial,sans-serif;">Advantages: <span style="font-family: Arial,sans-serif;">Disadvantages:
 * <span style="font-family: Arial,sans-serif;">The structure links the city of San Francisco, on the northern tip of theSan Francisco Peninsula, to Marin County.
 * <span style="font-family: Arial,sans-serif;">The bridge is popular with pedestrians and bicyclists as well as cars, and was built with walkways on either side of the six traffic lanes
 * <span style="font-family: Arial,sans-serif;">The Frommers travel guide considers the Golden Gate Bridge "possibly the most beautiful, certainly the most photographed bridge in the world".
 * <span style="font-family: Arial,sans-serif;">The operating cost and maintenance
 * <span style="font-family: Arial,sans-serif;">The suicides. More people die by suicide at the Golden Gate Bridge than at any other site in the world. By 2005, this count exceeded 1,200 and new suicides were occurring about once every two weeks. Various methods have been proposed and implemented to reduce the number of suicides.
 * <span style="font-family: Arial,sans-serif;">The wind conditions. Since its completion, the Golden Gate Bridge has been closed due to weather conditions only three times because the winds speed.
 * <span style="font-family: Arial,sans-serif;">Modern knowledge of the effect of earthquakes on structures led to a program to retrofit the Golden Gate to better resist seismic events. The proximity of the bridge to the San Andreas Fault places it at risk for a significant earthquake.