Essay on The Physics of a Truss Bridge

The purpose of the Boomilever Project is to build a cantilevered truss that is light-weight while still able to support 15 kilograms. With this project it serves to reinforce the cumulative concepts that have been taught throughout this semester of Engineering Statics. It has been necessary to research designs, types of wood, and types of adhesive that will create a final result that is consistent with the

Compression is the force pressing a material and compacting it and acts on the towers of a suspension bridge, this force is created from the weight of the towers and the load on the bridge. Compression forces will also act on the surface of the bridge deck as when a load is applied it will have some flexibility and bend, it will then travel up the cables, ropes or chains to transfer the compression forces to the towers. The towers then dissipate the compression directly into the earth. (Bagga 2014).

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

Each separate truss (of the dimensions 920x5x50mm) consisted of a Pratt truss with nine diagonal members on each side of the centre. The model was tested in sufficiently isolated condition by tutors. It successfully passed the initial weight test, and satisfactorily resisted horizontal forces. Once fitted onto the testing rig, loads were applied and increased incrementally. Slight deformation was observed before failing at 12.5 kg, at which force a collection of members failed in succession, concluding the test.

b. Describe the direction of the force and the meaning of the negative sign in the acceleration value.

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

In 1989, an earthquake caused the top deck of the bridge to collapse. This has raised concern in recent years in the case of a large scale earthquake. During an inspection in September of 2009, a 1.5 inch crack was found in a structural truss called an eyebar. The system of the truss is meant to distribute report will describe the tensile load from the weight of the bridge over 4 eyebars. One of them being broken, this same load was now distributed between only 3 eyebars. Because these eyebars were not designed to carry extra load, it became crucially important to repair the eyebar as soon as possible. However, because the bridge is so old, its mechanisms were more complex than what would be designed now in the current day. The engineering company C.C. Myers was contracted to do the repair. C.C Myers decided to repair the eyebar by welding a crossbar to the saddles which had been placed on each end of the broken eyebar (Alfrey, 2010). Four tie rods were then bolted to distribute the tensile load (Reid, 2010). This repair was completed in only 70 hours (Carlsen,

8. What stretch resulted in the highest contraction force? What happens to the muscle at the highest stretch levels?

Brunel’s solutions were groundbreaking and critics often questioned his designs. The Clifton Suspension Bridge had the longest span of any bridge in the world when it was completed; the Maidenhead Bridge was both the largest spanning brick arch bridge and the first to use a flattened arch form; and the Royal Albert Bridge was built using lenticular iron trusses.

A truss is a complex structure. Each piece needs to fit perfectly to perform its role, and anything less will mean that the truss will be unstable or simply does not hold an applied load. A truss bridge requires detailed construction and knowledge of how it distributes the forces. With the lack of this knowledge your truss could fail to withstand an applied force.

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).

13 x C-H (412) + 5 x C-C (348) + C-O (360) + O-H (463) + 9 x O=O (498)  12 x C=O (805) + 14 x O=H (463)

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