In this part of the chapter by Ching, he talks about the science of the structures. First, he explains that structural forces have vectors. All vectors must have 2 or more forces, magnitude, and direction. The sum of all vectors R, is represented by a diagonal line resulting from a parallelogram. And in a circular motion, all vectors lie on the tangent line. To achieve equilibrium in structural design the amount of tension must be equal to the amount of compression between forces acting against each other, which also supports Newton’s Law of action and reaction. Furthermore, he goes on to explaining columns. He explains that columns function best when they’re slender and rigid to support axial loads. They’re subject to bend when the compressive stresses are applied to the kern area. Columns, if they’re too long and slender or too short and thick, they are weak and subject to shortness and bending. He then defines beams as horizontal supports to loads. They too can bend if the elements supported are heavier than the beams can handle. Another way of deformation is the vertical shear of the column gets pushed forward. Trusses are defined as member of webs and chords supporting each other. Like columns and beams, frames and arched vaults can also bend if the line of thrust does not follow the arch axis. In the last part of his chapter he shows different examples of domes such as lattice, geodesic a d schwedler domes, with a note than they’re all steel. In addition, he provided many examples of connections between columns and beams, and explains that connectors can be either points, lines, or surfaces.