Figure 4 shows the slab model in this study, which consists of six concrete panels and two steel footing girders of I shape. Simplifying the model, there is no reinforcement simulated in geometrical information. They were all modelled with solid elements, in which the panels, as well as the panels and girders, are rigidly connected. To investigate the damage (deterioration)-induced modal property change, four cases in Figure 5 were considered and this study only investigated single panel damage: one intact case (labeled as Case 0) and three damage cases (Case 1, 2, and 3). Case 0 served as the reference, whose material properties for concrete and steel bars were set as those given by the design drawings, while Cases 1, 2, and 3 had their first (P1), second (P2), and third panel (P3) damaged, respectively, whose concrete material properties were tuned down (see Table 2). Steel bars were considered intact all the time. As mentioned previously, eigenvalue analysis was conducted for the four cases to obtain their modal frequencies and modal shapes.