LESSON 5: Trusses


There are two methods used to analyze trusses, the method of joints and the method of sections. In the method of joints you separate each member of the truss and analyze each joint individually. In the method of sections you make a cut down a chosen portion of the truss and analyze each side individually.

To begin analyzing a truss, when using either the method of sections or the method of joints, you should analyze the truss as a whole. Treat the truss as if it was a regular bar and analyze it to find any possible initial information. When you analyze the truss as a whole you can often find unknown values of vectors that support the truss.

Two of the more common ways of supporting trusses are through pin joints and rollers. The next two sections will feature an example problem of a truss supported by a pin joint and a roller. The pin joint will have 2 unknown supporting vectors,
one in the x-direction and one in the y-direction. This is because a pin joint stops the truss from moving in both of these directions. The roller will only have one supporting vector. This is because the roller only stops the vector from moving in the downward y-direction.

The next section will contain an explanation of how to use the method of joints, and the section after that will contain an explanation of the method of sections.