There is many reason that we need bridges in every day of our life, from sufficient means to pass over a roadway, waterway, railway, or other structure. You don’t even think about them because it takes no effort to get over them and they are just there for your use. So if you don’t think of them for everyday use I highly doubt that you would think of the physics that is involved in putting one together or the kind of force the bridge can actually take. I am going to show you the max force a truss bridge can take by demonstration it to you in class and also by trying to calculate it. I am also going to go over the many ways that truss bridges can fail and come to a tumbling crash. Before I get into the physics of the bridge you need to know what a truss bridge is and how it works. A truss is a structure composed of members connected together to form a rigid framework. Members are the load-carrying components of a structure. In most trusses, members are arranged in interconnected triangles, as shown below. Because of this configuration, truss members carry load primarily in tension and compression. Because trusses are very strong for their weight, they are often used to span long distances. They have been used extensively in bridges since the early 19th century; however, truss bridges have become somewhat less common in recent years. Today trusses are often used in the roofs of buildings and stadiums, in towers, construction cranes, and many similar structures and machines.
An easy way to understand how a truss bridge works is to use a nutcracker and a sting tied to the ends of the nutcracker. So even if you push down on the nutcracker it will not move or slide on the table. This is because the nutcracker is in equilibrium. I am going to show you a little of a harder way of calculating it with three triangles that are in the shape of a truss bridge so you can understand how the bridge works
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