Although Finley built more than a dozen small bridges, the first major bridge that incorporated his technique was built by Thomas Telford over the Menai Straits in England. Completed in , it had stone towers ft 47 m tall, was 1, ft m long, and boasted a span of ft m.
The roadway, which was 30 ft 9 m wide, was built on a rigid platform suspended from iron chain cables. The bridge is still in use, although the iron chains were replaced with steel bar links in Another American, John Roebling, developed two major improvements to suspension bridge design during the mids.
One was to stiffen the rigid deck platform with trusses arrays of horizontal and vertical girders that are cross-braced with diagonal beams. Experience had shown that wind or rhythmic traffic loads could send insufficiently stiffened decks into vibrations that could grow out of control and literally rip a bridge apart. Roebling's other important innovation involved construction of the bridge's supporting cables. Around , French engineers had shown that cables consisting of many strands of wire worked better than chains to suspend bridges.
Roebling developed a method for "spinning," or constructing, the cables in place on the bridge rather than transporting ungainly prefabricated cables and laboring them into position.
His method is still commonly though not exclusively used on new bridges. The history of suspension bridges is liberally sprinkled with examples of successful bridges that were widely believed to be impossible when proposed by a visionary engineer. One example was a railway bridge Roebling constructed between across the Niagra River gorge. The first truss-stiffened suspension bridge, it was supported by four 10 in cm diameter cables strung between stone towers.
Forty years after completion, the bridge was successfully carrying traffic 2. A steel worker lying cable stands for the suspension cable of the new Tacoma, Washington, Narrows Bridge on October 21, The Tacoma Narrows Bridge was the third largest suspension span bridge in the world and only five months old when it collapsed on Saturday, November 7, The center span, measuring 2, ft The suspension cables hung from the towers and were anchored 1, ft The designer, Leon Moisseiff, was one of the world's foremost bridge engineers.
Moisseiff's intent was to produce a very slender deck span arching gently between the tall towers. His design combined the principles of cable suspension with a girder design of steel plate stiffeners—running along the side of the roadway—that had been streamlined to only 8 ft 2.
Forced to endure undulations that pitched and rolled the deck, workmen complained of seasickness. After the opening, it became a challenging sporting event for motorists to cross even during light winds, and complaints about seasickness became common.
State and Toll Bridge Authority engineers were more than a little nervous about the behavior of the slender two-lane span, which was only 39 ft 1 1. Its shallow depth in relation to the length of the span , ft [2.
Engineers tried several methods to stabilize the oscillations, but none worked. By , Arkin saw that the wind velocity had risen from mi He and Farquharson halted traffic. Structural Failure Some bridges have in the past suffered from structural failure. This may be combination of poor design and severe weather conditions. When it was opened in , the Tacoma Narrows Bridge was the third longest suspension bridge in the world.
It later become known as "Galloping Gertie," due to the fact that it moved not only from side to side but up and down in the wind. Attempts were made to stabilize the structure with cables and hydraulic buffers, but they were unsuccessful. Eventually on November 7, , only four months after it was built the bridge collapsed in a wind of 42 mph.
The bridge was designed to withstand winds of up to mph. Some experts have blamed the collapse of the bridge upon a phenomenon called resonance. When a body vibrates at its natural frequency it can shatter. Before starting on how to build a suspension bridge , it necessary go look at the structural components of a suspension bridge, and for which purpose it is being used for. Suspenders, and anchorages which are fixed at both ends of the bridge to anchor the main supporting cables. The initial construction procedure of a suspension bridge involves the construction of the piers or towers following the traditional methods, that is, from foundation to superstructure.
In parallel with the construction of towers , the anchor blocks are fixed on both ends of the bridge in order to anchor the main supporting cables. Once the towers and anchor blocks are in place, the placing of the main cable will take place. The main supporting cables Catenary , consists of hundreds and thousands of thin wires which are then threaded individually by mechanical equipment , which are placed within two end anchor blocks. Once all the wires are placed, it is then tied together by wrapping it with steel wires and finally coating it with resin compound , to prevent corrosion.
After the main cables are constructed, the suspenders vertical steel short ropes are put in place from the main cables. Which generally varies in height and length smallest in middle span, to the largest in end spans, due to the parabolic shape of main cables.
Then the final phase of the construction starts , which involves placing the bridge deck. The bridge decks are generally placed in segments, each segments being prefabricated. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Prev NEXT. Civil Engineering. San Francisco's Golden Gate Bridge stands as a classic example of a suspension bridge. Cite This! Print Citation.
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