Design And Background Of Truss The Force

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

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.

Yarden: While creating our bridge our initial plans were much different than what our final product was. The more we worried about the strength of the bridge, the less time we had. We started off with the idea to have a truss bridge made of wood and cardboard. As shown here, (show picture from journal entry), but as the project progressed our ideas continued to change.

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

Clark Eldridge, an engineer from Washington State, had designed a trusted, conventional suspension bridge that would cost eleven million dollars. He requested that amount from the Federal Public Works Administration. However, Leon Moisseiff developed a design modification that would make the total cost of building the bridge much less- only eight million dollars. He swapped out the twenty-five feet long sturdy trusses as the form of support for the much cheaper alternative of 8 foot long girders, which were proven to be an insufficient form of support from the collapse of this bridge. His design accounted for an overall thinner bridge; and since his was the cheaper option, it was chosen for construction. However, the width of the bridge in comparison to the length, as well as the absence of trusses which would provide stability, are both part of Moisseiff’s “cost-effective”, yet impractically unsafe design. Since his design was flawed, he is mainly responsible for the bridge collapse. However, the board of engineers who approved his design are also partially responsible for the bridge collapse, as this unsafe design was allowed to be constructed. Meanwhile, it is imperative to remember that theories on aerodynamics were not fully developed as of the time that this bridge was constructed. Therefore, the full effect of oscillating forces was not properly accounted for due to the

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

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.

An arch bridge has a slight Bend in the middle that makes itself sturdy. Most arch bridge is as old as rock itself.A beam bridge is made of many different things mostly steel and prestressed concrete.A beam bridge is the simplest and the oldest bridge ever created. The beam bridge is so simple all it consists of is a log or we can go more advanced with steel and concrete. The beam bridge may be easy and inexpensive to build but is not the sturdiest. The beam bridge is Not sturdy because of the lack of materials used and that it is square. A beam bridge is made for depending on the place, long or short distances.Truss Bridges at the beginning were made of wood and iron . Most bridges were made of stone but the the truss Bridge was made of wood and iron because it can withstand a lot of tension unlike stone. Now a days truss bridges are made of metal. The truss bridge is a very strong bridge.The truss bridge is strong but is very very expensive and hard to build. The truss on the truss bridge is made to keep the wind from blowing it over.The truss is also to keep the tension from

Our group created a Pratt bridge design in order to maximize our efficiency with the limited amount of resources we were given. We also chose this type of bridge because it was simple and allowed for us to complete it within the given time frame. Our bridge was constructed using ⅛” x ⅛” balsa wood sticks, string, cardboard, paper, and a lot of hot glue. The balsa wood was used to make the frame, the cardboard was used to act as a level plane for the cans to stand on and as reinforcement for the sides of the bridge, and the paper and string were both used to construct the remaining roadbed. Balsa wood was used for the frame because it acts as a sturdy foundation. Cardboard was used as a level place to set our cans because of how smooth, flat, and sturdy it is. Cardboard was also used and attached to the sides of our bridge, as well as some of the joints, because it is very sturdy and does not pull apart or flex easily. Lastly, we used string and paper for the

In 1921, he submitted a preliminary design of a hybrid structure; which called for a 2,640-foot suspension span and two 685 foot cantilevered trusses. However, the design was met with much opposition; as many believed it to be an eyesore and felt that it would take away the natural beauty of the landscape. Eight years later, Strauss enlisted the help of engineers Othmar Ammann, Charles Derleth Jr., and Leon Moiuserff to redesign the bridge. By increasing the length of the suspension span to 4,000 feet, the engineers would be able to eliminate the need for a hybrid

In 1921, he submitted a preliminary design of a hybrid structure; which called for a 2,640-foot suspension span and two 685 foot cantilevered trusses. However, the design was met with much opposition; as many believed it to be an eyesore and felt that it would take away the natural beauty of the landscape. Eight years later, Strauss enlisted the help of engineers Othmar Ammann, Charles Derleth Jr., and Leon Moiuserff to redesign the bridge. By increasing the length of the suspension span to 4,000 feet, the engineers would be able to eliminate the need for a hybrid

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).

Truss Bridges are a common style of bridges used in the United States and all around the world. Some characteristics of truss bridge are joining a variety of relatively small structural members in a series of interconnected triangles. The vertical columns might work on tension and compression, but it depends on the dynamic loads that are applied and the complexity of the bridge. Many of the Howe truss were usually located in the North West part of the U.S because of the supplies available to them. The Howe truss was first introduced by William Howe in 1840 (Boom, Garrett. January 18, 2011.Garrett Bridges Howe Truss. www.garrettbridges.com).This style of bridge became very popular and was considered the best design to use in railroad bridges back in the 1800s. The lenticular truss is a unique design in which both the top

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