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Essay on suspension bridges
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A bridge is a structure that is used to cross an obstacle such as a river, a channel, a valley or a highway. The simplest kind of bridge is a tree trunk that has fallen across a stream or a set of twisted ropes and bamboo poles suspended (hanging) over a river. The latter is an example of early suspension bridges. Such bridges are still used in remote areas of many parts of the world like Asia, Africa and South America.
The modern, strong, sophisticated suspension bridges are the result of the work of a German-born engineer called John Roebling. He was the first to formulate the mathematics of these impressive structures and manufacture the steel cables that replaced the ropes of the early hanging bridges. He designed the first modern suspension
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The deck is the part of the bridge on which pedestrians and vehicles travel. It is a concrete and steel framework. It lies across an obstacle, a river for example, and rests on huge concrete blocks called abutments or anchorages on the opposite banks of the river. The piers are the concrete structures between the abutments. A suspension bridge must have at least one or two piers. These are the foundations of the tall towers on which the weight of the roadway and the vehicles is suspended or held up. This is made possible by the main steel cables which extend from the abutments on one side over the top of the towers to the opposite abutments. The ends of the cables are tightly entrenched in the abutments. The shorter vertical cables called suspenders attach the deck of the bridge to the main cables. Thus, although the roadway appears to be resting on the abutments and piers, it is actually suspended on the towers by means of the …show more content…
The two main forces are compression and tension. Compression is the force that pushes down on the deck. It comes from gravity, the weight of the bridge and the weight of the traffic that passes along it. Whereas compression is a pushing force, tension is a pulling force. The cables receive the tension force and transmit it to the towers and the abutments in which they are firmly embedded. This force is finally dissipated, spread out thinly, to the ground.
There are many other forces to consider in suspension bridge design. These include resonance (vibration or shaking) and torsion (a rotational or twisting force) caused by speeding traffic and strong windy conditions. The choice of construction materials is equally important. Only people can cross an obstacle on rope and bamboo suspension bridges. Early suspension bridges were not practical for moving heavy loads and traffic because of the weak materials. Iron is rigid, not resilient enough, and the more flexible steel has long replaced
Without a concrete reason for the bridge's failure, every suggested reason was researched until proven incorrect” (Silver). There were many reasons that were suggested, but could not be proven correct due to the collapse. Wikipedia states that “A small crack was formed through fretting wear at the bearing, and grew through internal corrosion, a problem known as stress corrosion cracking.” The failure of the bridge was caused by a defect in one of the eye-bars on the north side causing the other side to collapse as well. “Stress corrosion cracking is the formation of brittle cracks in a normally sound material through the simultaneous action of a tensile stress and a corrosive environment.
It became a link between Fort Erie, Canada and Buffalo, New York. The bridge is over one mile long, 5,800 feet, and holds three lanes of traffic. The center lane may go north or south depending on the volume of traffic. In 1934, the Great Depression caused a change.
Truss bridges can be built three different ways—as a pony bridge, through bridge, or deck bridge. A pony bridge, or a bridge in which the bracing is only on the sides and on top of the deck, are most often used when having a lighter load as there
On May 24, 1854, construction began of the Victoria Bridge. This was a difficult task for the workers given the size of the bridge (“almost two miles in length from shore to shore” ) was the largest construction project during this period of time. Moreover, the construction of the bridge did not cease during the winter months. Therefore, many of the workers on the bridge would continue even while the St-Lawrence River froze underneath their
The Bailey Island Bridge is located in Harpswell, Maine on Route 24. Before the making of the bridge, the fishermen that lived on Bailey’s Island wanted a bridge that connected their island to Orr’s Island. The town of Harpsweell made and voted on their decisions in the weekly town meetings (“Bailey”). The project was stalled because of some of the mainlanders in the town, but it was brought back up for discussion in 1912. They first agreed on a “road” which would connect the two islands and would be constructed with timber. This was to cost $3,000. The cost quickly reached $25,000 at a later town meting because they decided to build the bridge with stone and concrete instead. Once the legislature decided to pass a bill stating that it would fun state’s highway and bridge projects, they decided to move forward with the project (Hansen, 36).
At the time of its construction in 1929, the Ambassador Bridge was the largest spanned suspension bridge at 564 meters until the George Washington Bridge was built. It was an engineering masterpiece at the time. The total bridge length is 2,286 meters and rises to 118 meters above the river. Suspension cables support the main span of the Ambassador Bridge and the main pillars under the bridge are supported by steel in a cantilever truss structure. In total, the McClintic-Marshall masterpiece is comprised of 21,000 tons of steel. The immense socio-economical impact that the Ambassador Bridge has on transportation and trade is imperative for daily interaction between the Un...
Following the collapse of the I-35 Bridge, other bridges in the country, with similar construction designs, were scrutinized. According to federal statistics, more than 70,000 of the 607,363 or roughly 12 percent of the bridges in the United States are classified as “structurally deficient.”
Since humans are mortal, the sensation of pain is integral to the human condition. On one hand, pain alerts the body of a danger that is threatening its overall well-being; however, pain can be used as a means of torture to break the psyche or willpower of someone. As Lancelot races to save his queen from the evil Méléagant, he encounters the Sword Bridge. This Bridge is notorious for its slender construction, making it impossible for one
The 14-year construction of this urban landmark that stretched across the East River was completed in May of 1883. This was not only a bridge; it stood for many significant symbols. During this time period, the industrial aspects of things were at its peak and this represented the strength of the industry. Also it symbolized the use of immigrant workers and how much time and effort they put into making this bridge. Twenty seven men died while creating this bridge and that is something that most people forget when looking at the bridge, people risked there lives while giving a society that people needed. Not only that but it took tons and tons of steel and iron in order to complete this bridge and it was part of the steel and iron boom. This landmark led to the rise o...
The Tacoma Narrows Bridge is perhaps the most notorious failure in the world of engineering. It collapsed on November 7, 1940 just months after its opening on July 1, 1940. It was designed by Leon Moisseiff and at its time it was the third largest suspension bridge in the world with a center span of over half a mile long. The bridge was very narrow and sleek giving it a look of grace, but this design made it very flexible in the wind. Nicknamed the "Galloping Gertie," because of its undulating behavior, the Tacoma Narrows Bridge drew the attention of motorists seeking a cheap thrill. Drivers felt that they were driving on a roller coaster, as they would disappear from sight in the trough of the wave. On the last day of the bridge's existence it gave fair warning that its destruction was eminent. Not only did it oscillate up and down, but twisted side to side in a cork screw motion. After hours of this violent motion with wind speeds reaching forty and fifty miles per hour, the bridge collapsed. With such a catastrophic failure, many people ask why such an apparently well thought out plan could have failed so badly?(This rhetorical question clearly sets up a position of inquiry-which iniates all research.) The reason for the collapse of the Tacoma Narrows Bridge is still controversial, but three theories reveal the basis of an engineering explanation. (Jason then directly asserts what he found to be a possible answer to his question.)
This movement injects energy to the bridge with each cycle so that it overcomes the natural damping of the structure bring about a counter (negative damping) causing an exponentially growing response. In other words, the oscillations increase in amplitude with each cycle as the flutter velocity inserts more energy than the flexibility the structure can dissipate. Eventually this causes the bridge to fail due to excessive stress. Consequently the amplitude of the motion generated by the fluttering velocity increased beyond the strength of the focal point, in this case the suspender cables. On the event of failed suspender cables the weight of the deck shifted to the other cables causing them to break and making the central deck fall into the water below the
Other similar built bridges such as the Golden Gate Bridge in San Francisco can have vertical oscillations with amplitudes of up to 2 feet and horizontal oscillations up to 6 feet during severe windstorms(Levy, 1992). Due to visible oscillations in other similarly built bridges, oscillations in the Tacoma Narrows bridge were expected. However, the magnitude of the oscillations the bridge experienced and the length of time it took the bridge took to damp them out was of concern to the engineers involved. The length of time Tacoma Narrows Bridge needed to damp out its oscillations was unlike other similarly built suspension bridges, namely the Golden Gate Bridge, whose oscillations were quickly damped due to its larger width-to-span ratio. (need connecting sentence)Just before the total failure of the bridge the oscillations changed from their standard vertical and horizontal to a violent twisting motion, this twisting motion, which reached almost 45°, was what brought the bridge down. After a momentary lull in motion the twisting started up again and the bridge started to break, beginning with smaller suspender cables connecting the bridge deck and the 2 large main support cables. The breaking suspender cables meant that nothing was holding up that part of the bridge deck and it bega...
In her essay,”Importance of the Golden Gate Bridge,” Stephanie Stiavetti suggest that “It maintained this point of pride for nearly 25 years until the Verrazano- Narrows Bridge was built in New York in 1964. Today, this historic San Francisco landmark holds its place as the second largest suspension bridge in the country, behind Verrazano Narrows.” Back then, experts thought that it would be impossible to build a bridge across the tides and currents in that area because strong currents and tides would make construction extremely difficult and dangerous. The water is over 500 feet deep in the center of the channel, and along with the area's strong winds and thick fog, the idea of building a bridge there seemed nearly impossible. Despite all of the problems of building a bridge across the Golden Gate, Joseph Strauss was named as lead engineer for the project. Construction began January 5, 1933, and in the end cost more than $35 million to
When it comes to building a bridge, there are two main phases. First comes the engineering, designing, and planning of the bridge. Then comes the physical building of the bridge, a truly difficult task in the middle of a city over a highway. That being said, the flaw had to be made during construction. The bridge was designed to withstand a class five hurricane, earthquakes, and to last for over 100 years (Ahmed).
For this bridge its fall was inflicted by an unknown patron. One who’s identity or existence we never see verified. The record of the fall is short in the story described as only being for a moment. Then the bridge was finally introduced to “the sharp rocks which had always gazed up at me so peacefully from the rushing water”. Rocks gazing peacefully? This is almost as absurd as a bridge turning around. An action that the bridge itself cannot seem to believe it is doing. This attempt by the bridge was his final effort before his fall. I cannot even picture how a bridge would turn around and attempt to look on his back. The question that comes to my mind is how can a bridge see what’s on his back? If this book is trying to make us believe that this bridge is a human, or has human like qualities. Then how flexible a person is this bridge? Because I know very few people who can see whats on their back. Especially without turning so much that anything on their back would fall off. So is this bridge so inflexible that it breaks itself by turning around or is it trying to buck off its attacker unintentionally? This answer is never answered due to the story ending shortly thereafter this scene. With the short fall of the bridge onto the sharp rocks it had stared at for the entirety of its life. The events before and during the fall of the bridge was the main issue I had with my thesis that the bridge was