# Regional Seismic Damage Simulation of Corroded RC Frame Structures: A Case Study of Shenzhen City
## 5 Degradation Analysis of Building Interstory Backbone Curve Parameters
### Simulation of Corroded RC Frame Structures  
The corrosion condition of RC structures in coastal areas is complicated. In this section, two factors that can affect the seismic performance of corroded RC frame structures are considered in the simulation, which are the proportion of corroded components (PCC) and degree of corrosion.  
(1) Proportion of Corroded Components (PCC)  
The corrosion conditions of internal and peripheral components in an RC frame structures are completely different. The external beams and columns are in direct contact with coastal corrosive environment, which makes them more susceptible to chloride attack. Therefore, in this study, the peripheral beam and column components are assumed to be influenced by chloride attack and the degree of corrosion of peripheral components can be computed according to the method presented in Section 3. Meanwhile, the internal beam and column components do not have direct contact with the external environment and no corrosion is assumed for internal components (Figure 8). The proportion of corroded components (PCC) is defined as the ratio of peripheral column number to total column number.  
(2) Degree of Corrosion  
The degree of corrosion of components can significantly affect the seismic performance of RC frame structures. Therefore, the influence of degree of corrosion on the seismic performance of corroded RC frame structures is also investigated in the following numerical simulations.  
In this section, note that only two factors (i.e., PCC and degree of corrosion) are considered in the seismic performance analysis of corroded individual buildings. The actual corrosion condition of individual buildings can be much more complicated. For example, the bottom of columns can experience severe corrosion due to salinization of soil, and the peripheral components can experience non-uniform corrosion due to a higher chloride concentration on the outer surface of RC components [60].  
Figure 8: Design details of the RC frame structure.  
Furthermore, a simplified hysteretic model is used to simulate the performance of corroded RC frame structures. Some mechanisms, such as post-yielding buckling [62], can also affect the performance deterioration of RC frame structures, which require further investigation in future studies.  
In this section, typical RC frame structures with different PCCs and degrees of corrosion are investigated numerically. Specifically, four four-story RC frame structures with different pays are designed in compliance with Chinese code (GB50010-2010) [63]. According to the seismic intensity of Shenzhen, the adopted maximum value of the design spectrum acceleration is 0.8 m\(\cdot\)s\({}^{-2}\) and the rigid diaphragm assumption is adopted for the floor system. Note that the structural configuration and the design code adopted can also influence the seismic performance of corroded RC frame structures. Further works are required to investigate these effects.  
Pushover analyses are performed for all frames and the fixed boundary condition is adopted for all columns at the bottom. The structure-soil interaction in not considered in this study. The effect of structure-soil interaction can be considered in future studies according to related works [64; 65].  
Design details are shown in Figure 8 and the parameters of different simulation cases are presented in Table 2.