We now turn attention from tools and criteria for single elements to assemblies of elements. Trusses are a good place to start since they are one of the simplest form of assembly. Palladio knew this. Triangulation is the key to trusses. Using triangulation, it is possible to form a stable assembly with pin connections only.
Rectangles require moment-resisting connections to be stable.
The connections are more expensive to make, and the resulting moments require larger members. Classical Truss Theory A set of simplifying assumptions that make it easy to analyze trusses by hand, and to visualize how they work. Assume members are pin connected. Assume assembly is loaded at joints. Real structures often don't fit these ideal assumptions.