Figure 2
The diagram shows a schematic stiffness matrix K, presented in a square shape. The matrix is divided by a diagonal strip extending from the top-left corner to the bottom-right corner. The dots are marked near the top-left and bottom-right corners, which are labeled “K subscript P R.” The middle portion of the diagonal strip in light gray is labeled “K subscript R R.” Within the diagonal strip, two square hatched regions are visible. These hatched regions are labeled “K subscript Uppercase I R, lowercase i” and are positioned near the top left and bottom right sides.Schematic stiffness matrix K of the fully discretized model. Filled regions denote entries, which are not necessarily zero. The shaded regions, KIR,i with i = [1,2], are part of KPR and KRR due to addition of elements. Source: Authors’ own work