This chapter focuses on civil engineering building structures which have beams, beam-columns, bracing elements, shear walls, floor slabs, and rigid zones at structural joints. It discusses stiffness matrices for each element, assembly of system matrix, and condensation in depth with consideration of restrained, constrained, and free degree of freedom. Because the structural configuration is three-dimensional, vector formulation is introduced for generalized coordinate transformation. A structural model is established by first defining the location and orientation of each joint; then the elements that connect the joints are located and oriented. To define a structural model, three coordinate systems are essential: global, joint, and element. The deformation of one structural component or element can be very small relative to the deformation of adjacent components or elements. Thus the component or element with small deformation may be idealized as a rigid body. For a building structure, assembly procedure is more convenient to assemble the global structural stiffness matrix floor-by-floor.