## 1 Introduction  
In the past two decades, many studies on steel-concrete hybrid structures have been carried out [1; 2; 3]. Compared to either traditional steel or reinforced concrete (RC) structures, steel-concrete hybrid structures are more efficient and economical since they can effectively combine the advantages of structural steel and RC components. In practice, a huge number of high-rise buildings applied the steel-concrete hybrid structural system [4; 5; 6; 7]. Moreover, for industrial buildings, due to the limits of industrial requirements and special loads characteristics, the steel-concrete hybrid structural system has the unique priority to realize more flexible structural layouts [8; 9]. With the development of society and economy, more and more novel steel-concrete hybrid structural systems have been developed. RC tubular column-steel braced truss structure is a novel steel-concrete hybrid supporting structural system to house air-cooled condensers (ACC) in large-capacity thermal power plants (TPPs). As a water-saving cooling process in TPPs, ACC technique is widely applied in the coal-rich but water-shortage regions [10; 11]. Compared with the traditional supporting structure that consists of a series of A-shaped steel frames resting on a steel truss platform supported by an array of RC tubular columns, the novel supporting structure utilized steel diagonal braces to connect the steel truss and columns so as to further upgrade the structural safety performance. Figure 1 shows the photos of a practical supporting structure with steel diagonal braces. As a type of special and complex industrial structure, its main characteristics could be summarized as follows:  
1. Long-span and heavy-load structure. The height is about 60-70 m and the span is about 100-120 m. The vertical load is above 10,000 tons due to the large industrial units. 2. Steel-concrete vertical hybrid structure consisting of different substructures made of different materials. The lower parts are a series of RC tubular columns. The middle part is a steel braced truss, where steel diagonal braces are set between the lower chords of truss and the corbels of columns. The upper parts are a series of A-shaped steel frames, above 10 m-height. 3. Rigid-upper-flexible-bottom structure. Due to the characteristics of structural components and industrial requirements, the stiffness and mass are mainly distributed in the upper structure, resulting in the uneven distribution of stiffness and mass along the vertical direction. Taking these complexities and irregularities into account, in order to apply ACC technology in large-capacity TPPs located in strong earthquake prone regions, it is necessary to conduct a thorough study on the seismic performance of this hybrid structure. As we know, the pseudo-dynamic test (PDT) method is an effective way to investigate the seismic resistant capacity of building structures subjected to earthquake waves, and it involves online computers that are net worked with each other to control the input forces [12; 13]. With the PDT techniques, we can not only simulate the responses of large-scale structures subjected to earthquake, but also observe closely the seismic-resistant capacity of structures using slow loading procedures [14; 15]. In view of this, a series of pseudo-dynamic tests were performed on a 1/8 scaled sub-structure, and the general experimental results have been introduced [16]. However, due to the peculiarities of the structural system and limitations of the scaled model sub-structural test method, the seismic performance of this hybrid structure hasn't been clarified yet. It is known that the numerical simulation is another effective approach to investigate the seismic performance of structures, and significant progress has been made in the development of nonlinear analysis programs for evaluating the seismic performance of steel-concrete hybrid structures [17; 18; 19; 20; 21].