They are usually used in military engineering or in circumstances when fixed bridges are repaired, and can be so modular that they can be extended to span larger distances or even reinforced to support heightened loads. The vast majority of temporary bridges are not intended to be used for prolonged periods of time on single locations, although in some cases they may become a permanent part of the road network due to various factors.
The simples and cheapest temporary bridges are crane-fitted decking made out of construction wood that can facilitate passenger passage across small spans such as ditches. As the spans go longer and loads are heightened, prefabricated bridges made out of steel and iron have to be used. The most capable temporary bridges can span even distances of m using reinforced truss structure that can facilitate even heavy loads.
Moveable bridges — Moveable bridges are a compromise between the strength, carrying capacity and durability of fixed bridges, and the flexibility and modularity of the temporary bridges.
Their core functionality is providing safe passage of various types of loads from passenger to heavy freight , but with the ability to move out of the way of the boats or other kinds of under-deck traffic which would otherwise not be capable of fitting under the main body of the bridge.
Most commonly, movable bridges are made with simple truss or tied arch design and are spanning rivers with little to medium clearance under their main decks. When the need arises, they can either lift their entire deck sharply in the air or sway the deck structure to the side, opening the waterway for unrestricted passage of ships.
While the majority of the moveable bridges are small to medium size, large bridges also exist. The most famous moveable bridge in the world is London Tower Bridge, whose clearance below the decking rises from 8. However, bridges can be versatile and can support many different types of use. Additionally, some bridges are designed in such way to support multiple types of use, combining, for example, multiple car traffic lanes and pedestrian or bicycle passageways such as a present on the famous Brooklyn Bridge in New York City.
Pedestrian bridges — The oldest bridges ever made were designed to facilitate passenger travel over small bodies of water or unfriendly terrain. Today, they are usually made in urban environments or in terrain where car transport is inaccessible such as rough mountainous terrain, forests, swamps, etc. Since on-the foot or bicycle passenger traffic does not strain the bridges with much weight, designs of those bridges can be made to be more extravagant, elegant, sleek and better integrated with the urban environment or created with cheaper or less durable materials.
Many modern pedestrian-only bridges are made out of modern material, while some tourist pedestrian bridges feature more exoteric designs that even include transparent polymers in the decking, enabling users unrestricted view to the area below the bridge. Car Traffic — This is the most common usage of the bridge, with two or more lanes designed to carry car and truck traffic of various intensities. Modern large bridges usually feature multiple lanes that facilitate travel in a single direction, and while the majority of bridges have a single decking dedicated to car traffic, some can even have an additional deck, enabling each deck to be focused on providing travel in a single direction.
Double-decked bridges — Multi-purpose bridges that provide an enhanced flow of traffic across bodies of water or rough terrain. Most often they have a large number of car lanes, and sometimes have dedicated area for train tracks. For example, in addition to multiple car lanes on the main decking, famous Brooklyn Bridge in NYC features an isolated bicycle path.
Train bridges — Bridges made specifically to carry one or multiple lanes of train tracks, although in some cases train tracks can also be placed beside different deck type, or on different decking elevation. After car bridges, train bridges are the second-most-common type of bridges. First train bridges started being constructed during the early years of European Industrial Revolution as means of enabling faster shipment of freight between ore mines and ironworks factories.
With the appearance of safe passenger locomotives and cars, the rapid expansion of railway networks all around Europe, US and Asia brought the need for building thousands of railway bridges of various sizes and spans. Pipeline Bridges — Less common as a standalone bridge type, pipeline bridges are constructed to carry pipelines across water or inaccessible terrains. Pipelines can carry water, air, gas and communication cables.
In modern times, pipeline networks are usually incorporated in the structure of existing or newly built bridges that also house regular decking that facilitates pedestrian, car or railway transport. Pipeline bridges are usually very lightweight and can be supported only with the basic suspension bridge construction designs. In many cases, they are also equipped with walkways, but they are almost exclusively dedicated for maintenance purposes and are not intended for public use.
Aqueducts — are ancient bridge-like structures that are part of the larger viaduct networks intended to carry water from water-rich areas to sometimes very distant dry cities. Because of the need to maintain a low but constant drop of elevation of the main water-carrying passageway, aqueducts are very precisely created structures that sometimes need to reach very high elevations and maintain rigid structure while spanning large distances.
The largest aqueducts are made of stone and can have multiple tiers of arched bridges created one on top of each other. The modern equivalent of the ancient aqueduct bridges are pipeline bridges, but while the viaduct network used natural force of gravity to push water toward the desired destination, modern pipeline networks use electric pumps to propel water and other material.
Commercial bridges — These are bridges that host commercial buildings such as restaurants and shops. In the ASN, standards are hierarchically structured: first by source; e. View aligned curriculum. Do you agree with this alignment? Thanks for your feedback! Students take a hands-on look at the design of bridge piers columns. They determine the maximum possible load for that scenario, and calculate the cross-sectional area of a column designed to support that load.
Students are presented with a brief history of bridges as they learn about the three main bridge types: beam, arch and suspension. They are introduced to two natural forces — tension and compression — common to all bridges and structures. Students learn about the variety of materials used by engineers in the design and construction of modern bridges. They also find out about the material properties important to bridge construction and consider the advantages and disadvantages of steel and concrete as common bridge-building materials The students should have a familiarity with bridge types, as introduced in the first lesson of the Bridges unit, including area, and compressive and tensile forces.
We know that bridges play an important part in our daily lives. We know they are essential components of cities and the roadways between populations of people. Some bridges are simple and straightforward; others are amazingly complex.
What are some bridges that you know that might be called simple bridges? Possible answers: Log over a creek, bridges over streams. What are some bridges you know that might be considered more complicated? Possible answers: Golden Gate Bridge, other large bridges, bridges that carry both highway traffic and train traffic.
What makes some bridges simple and other complex? Possible answers: Their size, multiple purposes, environmental conditions, environmental forces, material maintenance requirements, etc. One amazing example of a bridge's contribution to connecting people to other populations and places for both social and commerce reasons is the Sky Gate Bridge connecting people to Japan's Kansai International Airport, located in Osaka Bay. It all started when the nearby Osaka and Tokyo airports were unable to meet demand, nor be expanded.
To solve the problem, the people of Japan took on one of the most challenging engineering projects the world has ever seen. Since they had no land for a new airport, they decided to create the Kansai International Airport by constructing an entire island! On this new, artificial island, they built the airport terminal and runways.
Then, they needed a bridge to access it. Spanning 3. Considered a modern engineering marvel, the airport and bridge opened in Four months later, it survived a magnitude 6. Because the airport site is built on compact soil, it sinks cm per year — another condition for engineers to consider in the ongoing safety and maintenance of the airport and bridge.
It is not easy to create a bridge the size of the Sky Gate Bridge. Have you ever wondered how engineers actually go about designing an entire bridge?
Bridges are often designed one piece at a time. Each pier columns and girder beams has to meet certain criteria for the success of the whole bridge. Structural engineers go through several steps before even coming up with ideas for their final designs. For designing safe bridge structures, the engineering design process includes the following steps: 1 developing a complete understanding of the problem, 2 determining potential bridge loads, 3 combining these loads to determine the highest potential load, and 4 computing mathematical relationships to determine the how much of a particular material is needed to resist the highest load.
One of the most important steps in the design process is to understand the problem. Otherwise, the hard work of the design might turn out to be a waste. In designing a bridge, for instance, if the engineering design team does not understand the purpose of the bridge, then their design could be completely irrelevant to solving the problem. If they are told to design a bridge to cross a river, without knowing more, they could design the bridge for a train.
But, if the bridge was supposed to be for only pedestrians and bicyclists, it would likely be grossly over-designed and unnecessarily expensive or vice versa. So, for a design to be suitable, efficient and economical, the design team must first fully understand the problem before taking any action.
Determining the potential loads or forces that are anticipated to act on a bridge is related to the bridge location and purpose. Engineers consider three main types of loads: dead loads, live loads and environmental loads:. Values for these loads are dependent on the use and location of the bridge. Examples: The columns and beams of a multi-level bridge designed for trains, vehicles and pedestrians should be able to withstand the combined load all three bridge uses at the same time.
The snow load anticipated for a bridge in Colorado would be much higher than that one in Georgia. A bridge in South Carolina should be designed to withstand earthquake loads and hurricane wind loads, while the same bridge in Nebraska should be designed for tornado wind loads. During bridge design, combining the loads for a particular bridge is an important step.
Engineers use several methods to accomplish this task. The Uniform Building Code UBC , the building code standard adopted by many states, defines five different load combinations. With this method, the load combination that produces the highest load or most critical effect is used for design planning.
The five UBC load combinations are:. As with the UBC method, the load combination that produces the highest load or most critical effect is used for design planning. For the purposes of this lesson and the associated activity Load It Up! Figure 1. Force acting on a column. It wasn't completed until after his death. It stands as an iconic representation of Victorian engineering and ingenuity — as does Brunel himself. Bridges all over the world are descended from the design and engineering of the Severn Bridge.
It has been instrumental in the socio-economic development of Istanbul and of Turkey. The 8. From Jacobs Arup, the new cable-stayed 2.
Another Dr Robin Sham marvel under construction.
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