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. After an engineer determines the highest or most critical load combination, they determine the size of the members. A bridge member is any individual main piece of the bridge structure, such as columns piers or beams girders. Column and beam sizes are calculated independently. To solve for the size of a column, engineers perform calculations using strengths of materials that have been pre-determined through testing. The Figure 1 sketch shows a load acting on a column.
This force represents the highest or most critical load combination from above. This load acts on the cross-sectional area of the column. In Figure 1, the area is unknown and hence the stress is unknown. Fy can be the tensile strength or compressive strength of the material. Typically, engineers assume that the tensile strength of concrete is zero. The area is easily solved for and is measured in square inches in 2.
Figure 2. Force acting on a beam. To solve for the size of a beam, engineers perform more calculations. The sketch in Figure 2 shows a beam with a load acting on it.
This load is the highest or most critical load combination acting on the top of the beam at mid-span. Compressive forces usually act on the top of the beam and tensile forces act on the bottom of the beam due to this particular loading.
Packets received on a trunk interface are forwarded within a bridge domain that has the same VLAN identifier. A Layer 2 trunk interface also supports IRB within a bridge domain. In addition, you can configure Layer 2 learning and forwarding properties that apply to the entire set of bridge domains. Packets received on a Layer 2 trunk interface are forwarded within a bridge domain that has the same VLAN identifier.
Help us improve your experience. Let us know what you think. Do you have time for a two-minute survey? Many people assume that the abutments ensure that the tied arch bridge and arch structure stay in place.
The best example of this is a bowstring which absorbs pressure, keeping both sides of the bow in contact, until it eventually flattens out. The structure of a stereotypical suspension bridge looks very simple but the design is extremely effective. The deck of the suspension bridge is the load-bearing element of the structure. This is held in place by vertical suspenders which support the cables. The suspension cables extend out beyond each side of the bridge and are anchored firmly into the ground.
It will depend upon the size of the bridge but a number of towers will be installed to hold up the suspension cables. Any load applied to the bridge is transformed into tension across the suspension cables which are the integral part of the structure.
Cables are connected from the pylons to the deck below. Either directly from the top of the tower or at different points of the column. When connected at different points of the column this creates a fan like pattern. This is the feature many people associate with cable stayed bridges. This type of structure tends to be used for distances greater than those achieved with a cantilever bridge design but less than a suspension bridge.
One of the main issues with this type of bridge is that the central connection of the cables can place horizontal pressure on the deck.
Therefore, the deck structure needs to be reinforced to withstand these ongoing pressures. If you look at the vast majority of expensive bridges you will see a pattern, they tend to be suspension bridges.
So, the answer to the question, what is the most expensive type of bridge to build is simple, a suspension bridge! There are a number of reasons why they tend to be so expensive.
Firstly they offer the ability to span huge distances up to feet — a span which is out of the reach of other bridge designs. The size of the towers, materials used and the installation of what is known as a deck truss beneath the bridge deck all add to the significant costs. We have come a long way from the first suspension bridges which were apparently made of twisted grass. From the point of view of strength, Truss Bridge provides the best strengh to weight ratio. In other words, it can hold the most weight per weight of its construction materials.
The section below goes into more detail. Even though the truss bridge design has been around for literally centuries it is widely regarded as the strongest type of bridge. The design itself looks extremely simple, so what makes it the strongest type of bridge and why? This is a load-bearing bridge which consists of an array of triangular structures.
Interestingly, the triangular beam structures are pinned in place rather than rigidly connected which is important when spreading the load. The vibrations caused by traffic moving over the bridge or even weather conditions are not isolated; instead they are spread right across the bridge structure, moving between triangular sections.
As the load is spread right across the bridge this also increases overall stability and reduces flexing. The Beam Bridge is the most common type of the bridge. It is also the simplest to build — please see the detailed description above. When you look at the different types of bridges and how they work, it opens up a whole new area of design engineering. What many of us assume to be an aesthetic feature of a modern day bridge is often an integral part of the design.
These features often help control tension and stress in a variety of ways. It is also interesting to see that different bridge designs are suitable for different terrains. The fact that many of these basic designs go back centuries says everything about their viability, durability and safety. You must be logged in to post a comment. Skip to content Home. Facebook-f Linkedin Twitter.
Types of Bridges.
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