## 1 Introduction  
Owing to an excellent seismic-resistant performance, light weight, and being easy to connect, steel beams are widely used as connecting beams or outer frame beams [1; 2; 3] in high-rise and super-high-rise hybrid structures. However, there are some defects in steel, such as poor fire resistance and instability, which hold back the practical use of steel members in industry [4; 5; 6]. On the other hand, steel can be quickly corroded, especially in extremely harsh environments (e.g., acid rain atmosphere), which will cause the decrease of strength, stiffness, and ductility and affect the seismic-resistant performance of the structure [7; 8]. Generally, there are three kinds of protection against corrosion, namely, surface-coating, the cathodic system, and the corrosion resistance of material, which is selected according to the structural type and the surrounding conditions. For instance, [PERSON] et al. [9] provided data of thickness loss in structural steel members under various catoptrical conditions and determined the effect of the material properties on the resistance to corrosion. Corrosion has been regarded as one of the five main damages in marine structures [10] and is induced by the thinning of structural material which decreases the strength capacity. A review of the protection against corrosion and the relationship between corrosion and a structural strength capacity can be found in [PERSON] et al. [11], particularly, in the marine environment. At present, there are some studies on the rebars corrosion in reinforced concrete structures [12; 13]. However, few studies on the seismic performance of the damage of corrosion in steel structures and members [14] has been reported. The corrosion damage of steel can cause the degradation of the structural mechanical properties [15; 16]. Therefore, the existing seismic analysis methods for undamaged steel members overestimate the seismic performance of steel members damaged by corrosion, which leads to a significant loss of property [17]. In order to develop a seismic computation analysis of structures during earthquakes, it is necessary to establish an accurate restoring force model of the structure members that is able to reflect the change of structural mechanical properties, such as the strength and stiffness degradation, and the reduction of ductility or the energy-dissipating capacity during an earthquake. The restoring force model consists of the skeleton curve and the hysteresis rule of members [18; 19]. The restoring force model can be divided into two categories, namely, a polygonal hysteretic (PH) model and a smooth hysteretic (SH) model, which are very important for the seismic analysis of structures. The most classical SH model is the Bouc-Wen model that considers the relationship between the stiffness, the strength degradation, and the hysteretic energy consumption [20; 21]. In the follow-up study, the Bouc-Wen model was improved further by considering the relationship of the stiffness degradation, the maximum displacement, and the effects of the loading path [22; 23]. Based on the experimental results of concrete members and the stress softening phenomenon caused by cyclic loading, [PERSON] et al. established an SH model that considers the effect of the reloading path and the cumulative damage [24]. In contrast with the SH model, the PH model has more advantages, such as a simple calculation, more obvious features in each stage, and more consistency with experimental observations. Therefore, the PH model is used more widely in engineering practice. The more classic PH model includes the bilinear and trilinear hysteresis models, which consider several factors, including the cracking of concrete, yielding, loading and unloading stiffness degradation, etc. [25; 26; 27]. In this paper, the polyline hysteresis model is adopted for the seismic analysis of corroded steel beams. The existing results show that there was a relationship between the surface roughness of the steel, the steel thickness, and the hysteretic energy.