# Effect Mechanism of Connection Joints in Fabricated Station Structures
## 1 Introduction  
The construction of urban underground spaces is developing rapidly in China, especially the subway rail transit, which has built 22 lines. The subway stations were designed and demonstrated to have good mechanical properties during the construction process. However, the damage phenomenon observed during the Kobe earthquake in 1995 [1], the Chi-Chi earthquake in 1999, and the Wenchuan earthquake in 2008 [2] indicated that the damage degree of underground structures caused by an earthquake is much higher than that of surface structures. The heaviest damaged one--Daikai station--suffered the total collapse of central columns over a length of 80 m. Furthermore, the station collapse resulted in ground settlement of 2.5 m. Therefore, the seismic study of underground structures is crucial [3, 4, 5]. Many scholars began to focus on the damage mechanism of subway stations represented by Daikai Station [6, 7, 8], and also showed the necessity of the seismic design of underground structures. For the study of the collapse and destruction disaster of the cast-in-place station, the two-dimensional numerical model was used to analyze the mechanical properties, which showed that the collapse of the station was caused by the shear failure of the central column [9, 10, 11]. Since the two-dimensional model can only consider the middle column as a continuous wall, it cannot reproduce the collapse process of the Daikai station. A 3D finite element numerical analysis was used to simulate reinforced concretestructure, analyze the collapse mechanism of Daikai station, and reproduce the failure process [6; 12; 13]. Numerous analyses and investigations found that the center column was the weak location of the cast-in-place frame underground structure [14; 15; 16]. Many scholars carried out a large number of seismic design studies of the center column by installing isolation bearings to absorb seismic energy or changing the constraint conditions [17]. At present, the commonly used bearings mainly include rubber bearings and sliding bearings [18; 19; 20; 21]. Up to now, the research on seismic design of cast-in-place station structures has been very detailed. However, the construction method of cast-in-place structures has a significant influence on the environment. Meanwhile, winter construction can face a shutdown period and reduce efficiency. The construction method of fabricated structures can obviously change these situations and conform to the social and economic strategy of energy conservation, environmental protection, and sustainable development. The construction method was successfully applied in constructing subway stations in Germany, Russia, and other countries. The Kyoqiao station of the JR Kyoye Line in Japan was built using double-circle shield tunneling. The Platinum station of Tokyo Line 7 was constructed using triple-circle shield tunneling [22; 23; 24]. The Jiangtai Station in Beijing was built using single-circle large-diameter shield tunneling and PBA [25; 26; 27]. In recent years, China has been speeding up the construction of prefabricated station structures. Five underground stations, including Yuanjiadian station [28] and Hongqi Street Station, were assembled and constructed in Changchun Metro Line 2. Although prefabricated station structures are in full swing, the seismic design of fabricated station structures is still lacking. [PERSON] and [PERSON] [29; 30] conducted axial bending test research on the connected joints of prefabricated components and found that the initial stiffness of the joints was large and the flexural stiffness increased with the increase of axial force. Taking Yuanjiadian station structure as the research object, [PERSON] and [PERSON] [31; 32; 33] comparatively studied the differences in internal force and deformation between the fabricated and cast-in-place structures through experimental and numerical analyses. The fabricated station structure has better energy dissipation capacity than the cast-in-place station structure, but the lateral deformation resistance is weak.