How To Build Suspension Bridges

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.

All are very effective and work well if built in the right conditions. The thing that separates these bridges from one another is that they all have different points of compression and tension. Tension is two forces of opposition that pull away from each other to keep it from being pulled together. If you imagine a rope in a game of tug-of-war, the rope has a lot of tension because it is being pulled apart, but the opposing force inside of the rope is trying to keep it together. The same can be applied to a bridge truss because the tension truss is opposing the compression truss by pulling the bridge apart. Tension also pulls the platform of the bridge by stretching it to keep the bridge from collapsing. Compression is two forces in opposition that push an object together to try to compress it. If you think of someone standing on a soda can, the soda can tries to resist being squished, but the weight of the person standing on the can still squashes it. This example can also pertain to the truss on a bridge. A compression truss opposes the tension truss by pulling the bridge together. Compression is also placed on the top of a truss and in its bases. The compression at the top of the bridge counteracts with the tension of the platform and balances out each force. The compression in its bases is from the weight of the platform and trusses. Bridge engineers calculate the tension and

Bollman truss had many independent tension elements that makes a strong bridge which is easy to assemble.

When the bridge was tested, at 26 pounds of pressure, it began to buckle. The top support near the middle of the bridge on one side caved in, and as the weight increased, more of the top supports collapsed. At 47.3 pounds of pressure, the bridge snapped in half. By the end of the testing, the bridge had lost all of it’s top supports, two sections of diagonal supports on either side, and a small portion of the roadway.

The second bridge I will be talking about is the Batman Bridge. The Batman Bridge is a cable-stay bridge

Trusses are triangular shaped support beams that attach point-side down to the roadbed of the bridge on either side. This structure distributes the force of the weights to the bridge. These bridges are a lot like beam bridges, but stronger and it is perfect for heavy loads and small distances. In addition, triangular trusses will work, but will drastically decrease the weight or load your bridge can hold. (To make your bridge even stronger, attach short pieces of spaghetti to the points of the trusses to make small triangles - trusses for the trusses.) Also, the triangular shape is the best method of construction than rectangular shape as there is no bending because the bridge is strong.

Design Elements: While building this bridge, the first design element, was the deck design. We took around one horizontal length of vertical popsicle sticks and lined them side by side, and repeated. Later we connected them together with a horizontal popsicle stick. I then took two lines and placed them ontop of eachother to create a flat surface. This way it will carry a lot of weight, and it will also run smoothly. After this I created trusses to put on the side, so that the weight would be evenly distributed amongst the bridge, instead of all the weight on one part. This would help stop the bridge from immediately bending once weights were put into the bucket. To make the trusses I had to take popsicle sticks and glue them into a triangle shape, and then glue them together from the bottom. This way they wouldn’t break apart. I then doubled them up so that it would be able to sustain more weight. Under the bridge I placed a lot of beams, so that the bridge would hold together from the bottom, instead of immediately bending once I placed a weight. I made the beam from gluing

Kaylie Griffin and I chose to build the Clifton Suspension Bridge. The Clifton Suspension Bridge is a suspension bridge located in Bristol, United Kingdom. A suspension bridge is a type of bridge which the deck is supported by cables that hang vertically off larger cables or hangers. Suspension bridges typically have two towers and are anchored to abutments at their ends.The towers help to support much of the weight that crosses the bridge’s deck, such as cars and people. The towers also dissipate the load directly into the planet Earth. These features of a suspension bridge are why they are strong therefore, one of the more popular designs for a bridge. When building our popsicle bridge, we had to add x shaped joints and brackets to help our

Wind loads, where in some cases it may be necessary to consider the aeroelastic interaction between wind and bridge, leading possibly to aerodynamic instability;

There are only a very few limitations in the use of plate girders. Compared with trusses they are heavier, more difficult to transport and have larger wind resistance. The provision of openings for services is also more difficult. The low torsional stiffness of plate girders makes them difficult to use in bridges having small plan radius. Plate girders can sometimes pose problems during erection because of concern for the stability of compression

The initial design of the truss bridge shows trusses that are symmetrical throughout the bridge which allowed the weight of the truck moving across to be spread evenly throughout the bridge, allowing it to be stable when the weight is added resulting in minimal deflection of the overall bridge. Throughout the process, most supporting beams were mainly solid bars as they are good in tension and are more sturdy giving the bridge stronger structure. Other beams that didn’t take much load were changed to hollow tubes to lower the cost as well as hold the tensile load of the bridge, this overall reducing the cost and making the bridge more sturdy.

Parabolas are used throughout the world to make life easier and more enjoyable for people. They are used in everything from practical items like car headlights to grand iconic landmarks like the eiffel tower, but most importantly they are used in suspension bridges allowing large numbers of people to access new places easily. For these reasons we decided to create a model suspension bridge to display the usefulness of the bridge and the parabolic shape as a whole.

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).

The Tacoma Narrows Bridge was designed for a wind speed of 100 miles per hour and a static wind pressure of 30 pounds-force per square foot but unfortunately the bridge failed at a wind speed of less than half and a static wind pressure of one-sixth (Delatte, 2009). This phenomenon raises a big question mark on how this is possible. At first, resonance was suspected to be the main cause of the bridge failure (The New York Times, 1940). After some proper research and thorough investigations by engineers, they came up with several theories on how did the bridge collapse. The primary cause of the collapse lies in the general proportions of the bridge and the type of stiffening girders and floor. The ratio of the width of the bridge to the length of the main span was so much smaller and the vertical stiffness was so much less than those of previously constructed bridges that

Superstructure bears the load that is being passed over the bridge and it transmits the forces caused by the same to substructure. Load received from the decking is transferred on to the substructure by Bearings. They also distribute the load evenly over the substructure material as it may not have sufficient strength to bear the superstructure load directly. Piers and Abutments are the vertical substructures which transfer the load to the earth in the foundation. Wing walls and returns are constructed as the extension of