###### Abstract
Such evaluation of the impact of concrete and rebar deterioration often requires an onsite investigation. However, according to the methodology presented in FEMA 310, which does not specify a quantitative analysis procedure, the seismic evaluation of RC structures including the impact of corroded members is based on empirical judgment. Meanwhile, the seismic performance of existing RC buildings for each floor and each direction is evaluated as per the Japanese seismic evaluation standard [9] using the Equation (1):  
\[I_{s}=E_{o}\times S_{D}\times T \tag{1}\]  
where \(I_{s}\) = structural performance index, \(E_{o}\) = basic structural performance index, \(S_{D}\) = irregularity index, and \(T\) = aging index. Here, \(E_{O}\) is the basic structural performance index calculated in view of the ultimate horizontal capacity, deformation capacity, number of floors, and a specific number of floors, and \(S_{D}\) (non-uniformity index) is the distribution of stiffness according to the irregularity of the building shape and height. \(S_{D}\) (irregularity index) is a supplementary index to adjust \(E_{O}\) by considering the irregular architectural morphology and irregular distribution of building height and stiffness. Finally, \(T\) (aging index) is a supplementary index to evaluate the age-dependent deterioration of building. \(T\) is an index that evaluates the impact of structural deterioration or aging through a systematic onsite inspection consisting of initial inspection, follow-up inspection, and additional elaborate inspection. In the initial inspection, \(T\) = 0.8 is applied to a building of minimum 30 years, and \(T\) = 0.9 when the interior finishing materials of the building are noticeably peeled off. Among the T values obtained from the onsite inspection, the minimum T value is finally multiplied by the E\({}_{O}\) index. In the follow-up inspection and additional elaborate inspection, \(T\) of the entire building is calculated by applying the summation principle to \(T_{i}\) of individual members inspected on each floor, where \(T_{i}\) denotes the aging index of the number of inspected floors by the number of floors. Here, \(T_{i}\) represents the aging index of the number of floors (i) inspected. For example, the seismic performance of RC buildings with rebars is evaluated as follows: in the case of beams, if more than 1/3 of all members inspected from each direction have corroded bars, \(T_{i}\) = 0.05; if it is 1/9-1/3, \(T_{i}\) = 0.017; if \(<\)1/9, \(T_{i}\) = 0.006; and if 0, \(T_{i}\) = 0. In the case of columns, the corresponding \(T_{i}\) values are 0.15, 0.057, 0.017, and 0, respectively, as shown in Table 1.  
Compared with FEMA 310 and 356 guidelines, the Japanese seismic evaluation standard uses \(T\) for quantitative evaluation of seismic performance of RC buildings with corrosion-damaged members. However, it is not a direct evaluation method based on E\({}_{O}\) used to modify Is and the structural performance degradation factor that considers the strength-ductility correlation of \(T\) of corroded members; it is an indirect evaluation of the impact of members with corroded bars on the overall seismic performance of buildings. As described above, according to the current standards and guidelines for seismic performance evaluation of RC structures, the strength and deformation of the structure itself are mainly evaluated using primarily a structural analysis program based on structural drawings and measured material strength. That is, the reduction in the durability of corrosion-damaged RC members is addressed by an indirect or qualitative method instead of a direct or quantitative method. Thus far, hardly any research on the seismic performance evaluation based on the impact of corroded RC members has been conducted [6; 10], not to mention research on the quantitative structural performance degradation factor based on the correlation of the strength-deformation capacity of corroded members relative to intact members.