## 1 Introduction  
Precast concrete (PC) buildings have been developing vigorously worldwide in recent years, and have become an alternative to traditional RC buildings [1]. Chinese government departments also issued a series of policies to force the PC buildings to reach a certain proportion in new built structures [2], so as to promote the development of PC buildings and the transformation of the construction industry. In the past, the prefabrication method was mainly used to construct some low-rise industrial plants and temporary houses [3]; the seismic grade of such buildings was not high,so the demand for seismic performance was also low. The prefabrication method satisfies the original intention of rapid construction and cost saving of such buildings, so it had good applicability. As for residential buildings, precast floor systems with masonry walls were widely used in China, but the lack of effective connection among various parts led to insufficient integrity, and together with irregular construction and other problems, huge drawbacks were exposed in the Wenchuan Earthquake [4]. Since then, Chinese engineering designers have begun to rethink the seismic performance of PC buildings. At present, PC buildings are expected to meet the same requirements as RC buildings under the same site conditions, which is an inevitable challenge in their development. The seismic performance of PC buildings is directly affected by the connection behavior of prefabricated components [5]. Among various connections, the beam-column connection is most critical to frame structures, which is also the focus of current experimental researches. There are generally two perspectives about the design of beam-column joint, which are summarized as using emulated connections and non-emulated connections. For emulated connections [6], although the structural forms are different, the materials used are almost the same. Pouring a certain amount of concrete is required to guarantee the integrity of the joint. Designers only hope to achieve its nonlinear performance as close as possible to the RC joint through changing some construction details. Therefore, the design concept of \"equivalent cast-in-situ\" comes into being, and the RC joint is the only evaluation criterion for emulated connections. For non-emulated connections, designers hope that through a new material, new technology or a new force mechanism, the nonlinear behaviors of the joint can be distinguished from the RC joint with unique advantages. Such a connection generally does not require a large amount of concrete pouring to ensure the reliability. Due to the different design intention, the RC joint can only be used as a reference when evaluating the performance of non-emulated connections, and do not have any practical comparison significance. The emulated connections can be divided into multiple forms according to the position of the post-poured concrete. It is a good design idea to place the post-cast area in the beam mid-span to make the beam-column junction which bears complex forces have good integrity (Figure 1a) [7]. However, such a method is hardly used in recent years due to the inconvenience of fabrication, transportation and hoisting of special-shaped components. The more commonly used connection method is to place the post-cast area at the beam-column junction, so that the precast column can serve as an effective support for beams thus to reduce the use of formwork [8]. Such a connection, which relies on precast columns to bear the construction load, can be further divided into two types: shear keys at the beam end (Figure 1b) [9] and U-shaped keyway at the beam end (Figure 1c) [10], of which the precast columns can also be made into multistory columns [11]. There is also a form in which the core area and the beam in one direction are precast as a whole, and connect the beam in the other direction through sleeves at the beam end (Figure 1d) [12].