This report aims to examine the advantages and shortcomings of four different types of bridge, namely the truss, suspension, beam, and cantilever bridges. Secondly, it evaluates three forces that act upon these bridges ㅡ compression, tension, and shear ㅡ and how each kind of bridge handles the forces. Lastly, it includes a explanation of the Tacoma Bridge incident and a description of the author’s bridge.
Since tension, compression, and shear are to be discussed for each kind of bridge, here are definitions for those forces. Tension acts to expand or lengthen the thing upon which it is acting (Basics). Compression, the opposite of tension, is a force that attempts to compress or shorten whatever it is acting upon (Basics). Another force, shear, occurs when two forces move in opposite directions on the bridge (Discovery).
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In the middle parts of these bridges, there is only one side support, making it weaker than other sections of the bridge (NYLN). On this type of bridge, tension and compression are the main forces. When there is a load, the bridge experiences tension in the upper part of the cantilever span and compression in the span under the deck (Hagler). As long as these forces remain balanced, the bridge functions well, but, for example, if the compression force becomes more than the tension force, then the lower supports of the bridge could collapse (Hagler). Though not as prominent a force, shear still acts upon cantilever bridges when a load passes along the “suspended deck;” since the deck is not supported by a beam underneath and has only one side support, it is the weakest point of the bridge (Hagler). The load, in addition to gravity, pushes downward while the beams on either side of it push back upwards; the cantilever of the bridge distributes this force on the deck so that it does not collapse
A simple beam bridge that is flat across and supported at the two ends. A longer beam bridge can be held up along the middle by piers standing in the river. The weight of the bridge itself, plus the load that it carries, plus gravity are the downward forces are spread evenly across the length of the bridge. The upwards forces that hold the bridge up come from the piers. The Confederation Bridge in Canada is a famous beam bridge.
Calculations were performed to determine the effectiveness of the design of the platform. Allowing for a safety factor of 1.5 times the design weight of 10kg and considering the bridge must not be overdesigned; plans were made for the bridge to fail at 25kg, 2.5 times that of the design weight. According to the calculations, the bridge would hold a load of over 15kg and experience failure at 20kg in the members. These calculations were later disproven in the testing, breaking 8kg earlier than expected, due to unforseen errors. An analysis of the bridge design and calculations has been included at the end of this report.
In Washington, the Interstate 5 bridge, which crossed the Skagit River, collapsed last month. The damage of this accident included two cars broke and three persons injured. According to officials, the bridge fell into the river after the large truck hit a beam. The bridge had a risky condition called facture critical. The U.S has a lot of bridges; however, nearly two thousand bridges were built between the middle of 1950s and the 1970s, so those ones are obsolete bridges. In addition, back then, the government cut corners in bridge buildings to cost reduction. Although gas and diesel taxes attempted to allocate to restored the bridge, the government cloud not collect money enough to repair the bridge because people began to use efficient vehicle.
The report debates the Tacoma narrows bridge failure and the different theories of how it came about, using information about what type of bridge it is and the forces acting on it before and during the collapse. It also discusses ways in which the failure could have been avoided, from changes in the design to modifications to the bridge after its construction.
Initially, suspension bridges before 1940 were made of piers, towers, wires, anchorages, and roadways. Piers were the main foundation for the suspension bridges. There usually were two of them, which were made out of cement and were entrenched in ground underneath the body of water that the bridge was spanned across. Towers were built on top of the piers to provide a means of connection for the roadways and wires. Wires were connected to the towers, roadways, and anchorages to provide tension support for the weight of the bridge. The anchorages were large cement platforms that were planted into the ground on either side of the land so that the wires could be connected to it. Lastly, the roadways were the main point of the suspension bridge. They usually were wide enough to provide four lanes of traffic and stretched from one side of the bridge to the other. This was the basic design of the suspension bridges
Since the early days, the men try overcome environmental challenges and, in this process, ends up creating amazing masterpieces of engineering. Among this works, the bridges appears as the clearest representatives of how the mankind could adapt to Earth’s contours. If the shape of landscape can’t be changed, the bridges are the solution to link two places and allows the connection of the traffic to improve aspects such as the communication and the trade. Depending to the need, to the sources and to the environment, the bridge can be constructed in a specific configuration. There are five main sorts of bridges configurations. First, there is the simplest bridge, the beam bridge. Second, the arch bridge, one of the oldest kind. There are the truss, composed of set of trellises. Lastly, there are the cable-stayed and
Bridges are a vital part of people’s everyday life and without them people would not be able to do nearly as much as is possible today. The weather in the outer banks of North Carolina is very rough and can be very detrimental to the various structures on them. When hurricanes come near North Carolina the outer banks are hit the worst. Bridges on the outer banks keep being destroyed by weather and so the people there have to think about the cost, the effectiveness, and the need between a strong expensive bridge that will be able to handle rough weather or a cheap quick to build bridges that may fall with any extreme weather.
It is shaped in a way to transfer weight to the towers and anchors with its tension (O'Connor, 1971, p. 372). Cables are made of high strength wires spirally bound to form a rope (O'Connor, 1971, p. 372). Vertical cable suspenders that are fastened to the main cables hang the actual roadway. Stiffening girders and trusses are along the side of the bridge to distribute concentrated loads and help to keep the motion of the bridge at a minimum (Troitsky, 1994, p115).
When bridges are poorly constructed, they may fail due to load they carry, collision by derailed trains or even by vehicles that lose control leading to catastrophic incidences. However, if bridges are well-constructed, the chances or injury are greatly minimized in the event of an accident. Discussed in the subsections are the requirements of AS 5100 standards in relation to cable-stayed bridges and include design requirements for bridges, bridge aesthetics, bridge functional requirements, bridge component design requirements and bridge construction
Hecox (2011) says that the arch structure of the Tillman Bridge makes the canyon walls hold the weight of both vehicles and the bridge itself. In addition, the arch structure allows a better vision of the canyon for the drivers, which was a request of the population to the engineers of the project. In the other hand, according to Jones (2015), the truss structure of the new St. Anthony Bridge also was requested by the population because they wanted to keep a truss bridge in that place. The author also affirms that the St. Anthony Bridge is a truss, but the project team proposed adding a posttensioned concrete bottom chord to the steel truss in order to reinforce it. The project team made this choice because one bridge in Minnesota has collapsed in 2007, and the engineers wanted to lessen the fracture-critical issues to avoid a new catastrophe. In addition, this posttensioning approach wiil make the structure redundant for both resiliency and long-term durability. In conclusion, both bridge's structures were right chosen in order to provide safety and beauty in both
The Principle upon which all trusses rely is that the triangle is the strongest and most rigid geometric Figure. By arranging the framework of triangles in patterns that varied from designer to designer, the structure acquired different appearances and served different purposes depending on the needs of bridge builders. The pony truss, the smallest type and ordinarily confined to lengths under 140 feet, with most under 100 feet, is distinguished by its low profile and absence of bracing above the roadway. The through truss by comparison is greater in length and height and consists of a tunnel-like structure that carries traffic through a system of overhead bracing which ties together the upper chords of the bridge.
The Pratt truss bridge was originally founded by Caleb and Thomas Pratt in 1844. It is mainly used to carry trains. The biggest advantage of this bridge was its low costs for construction and the materials to construct a truss bridge are minimal. It also use materials that is cheaper and light in weight. We can easily identify a pratt truss by detecting its diagonal members, which (excluding for the very end ones) all slant down and in toward the center of the span. The pratt truss was designed by applying few laws that related to the mechanics of materials concept. The bridge is mainly built using steel girders to support the construction of the structure. The below part of bridge weight is high so, it need an enough support to prevent from
The structure of a truss bridge is, by design, large and spanning a large gap. The interconnecting triangular components need to be large to bear and distribute heavy forces applied to the truss. This means in certain conditions (restricted spaces), the truss bridge may not be the best option.
Because of advancements in today’s technology in construction field, many types of bridges are being constructed depending on the requirement and their suitability for the situations.
There are many differences between our bridge and other bridges. One being location. Another one being that thing that was sacrificed for it. Another one being cost. Also another difference would be weight and capacity, and the size or length.