Truss Bridge Report free essay sample

Objective The objective of the project is to build a truss that would be able to take a specific amount of downward force remarkably with respect to the weight of the truss itself, i. e. to construct a truss that would hold a relatively high efficiency score. And construct the bridge in such a way to as to keep the deflection of the structure at minimal. Introduction First of all, what is a truss? In an engineering view, a truss is a structure that is made up of series of triangular unit made of straight members that are connected at junctions known as nodes. External forces created by bodies known as loads, are often placed on areas of the structures which then creates internal forces in the members in form of either a Tensile Force or a Compressive Force. The practical analysis was carried out to help better our understanding on the theories behind the behaviour of a truss under different circumstances. We will write a custom essay sample on Truss Bridge Report or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Analysis A Pratt truss illustrating the arrangement of the bars By calculation The length of the horizontal member is 99. 4m The height of the bridge is 20m. And the diagonal members are all 23. m The distance between the two sides (floor Beam) was 16m. Materials Today, bridges can be of the span, arch, or suspension type. Materials used throughout history include wood, masonry, cast iron, wrought iron, concrete, steel, reinforced concrete, alloy and silicon steel, pre-stressed concrete, carbon fibre, and aluminium. But since the experiment was to be performed in a small scale, Popsicle sticks where chosen to do the job. Then a non-toxic adhesive was chosen to be used to join the members at the node. A clamp of some sort is a good idea when constructing. Clamps are important because most of the popsicle stick arent flat, so if you dont clamp them when you glue them together your bridge probably wont hold together very well. Procedure The bridge truss was constructed using about 140 sticks, give or take a few. We began the construction by creating the smaller pieces that would be easier to glue together, clamped the pieces together, and then left them dry for over a period of 7 days, which made them strong enough to be used. We started with each side of the bridge, in order to keep them symmetrical, then flipped each side and added more members to strengthen the sides. We then erected the constructed sides and added angled supports across the horizontal member at the bottom, and then added some centre support to hold the structure firmly and give it its shape. We then added some horizontal members to connect the sides together and minimize the deflection of the structure. And we levelled the structure with a horizontal surface after gluing any major part to give it a stable composition. Then after the assembly process was complete. We then gave the bridge structure as a whole, time do dry so the glue would dry and give the joined members and nodes time to dry. Then it was on to the testing Testing For the testing procedure, the bridge was placed between two horizontal surfaces at a height that was enough to place weights to the lower horizontal members. And then weights were added simultaneously to the center of the lower horizontal members on both sides so as to balance the weight distribution across the bridge and keep it at equilibrium throughout the test. Then weights in newton were added continuously to the members until the structure began to show signs of major deformation that could destroy the bridge structur. Then the maximum weight it could take was noted down by the supervisor in charge of the testing procedure so that the grades would be allotted accordingly. Discussion As mentioned earlier a truss is a structure that is made up of one or more triangles connected at joints referred to as nodes. For the experiment we chose to use a type of truss known as a Pratt Truss. We chose this type of truss because of its history. It has been in use since the practice of using of wood for the construction of bridges was brought into play, and still when wood gave way to iron, and remained when iron gave way to steel. The vertical members in this type of truss are under compression, while the horizontal members respond to tension. It is unique because the long diagonal bars are only in tension for gravity load effect, which allows the members to be used more efficiently, so that slenderness effects related to buckling due to compression loads will not control the design. The prat truss which was patented in 1844 was patented by Caleb Pratt and his son Thomas Willis Pratt. Conclusion To sum it all up, according to the analysis of the truss, the theory was confirmed that the Pratt truss is one of the best trusses for withstanding vertical loadings, because of the geometry of the members.