## 1 Introduction  
Various civil engineering structures have been constructed spurred by global industrialization and economic growth. Many of these structures are aging and require strengthening or replacement to prevent accidents and disasters. The process of replacing these structures must ensure minimal traffic congestion, minimal impact on the surrounding environment and economy, and stability of the structure during its replacement. To meet these demands, assembled structures using precast concrete are actively being studied and built. The precast concrete modular construction method uses precast concrete modules that are manufactured by factories and assembled onsite. This method is widely applied to civil engineering and architectural structures. For example, in the USA, the accelerated bridge construction (ABC) method was proposed and developed to replace old bridges and respond to the demands for new city structures [1].  
Because precast concrete structures are a type of reinforced concrete, their bending and shear strengths need to be reviewed to determine their stability and serviceability in the event of crack development and structural deflection. In addition, the resulting joints between the modules need to be analyzed to determine their behavioral characteristics and to ensure the stability and serviceability of the structures [2; 3; 4].  
Various studies have been conducted with the aim of ensuring joint stability. In one study, shear strength and deformation behavior were evaluated using two types of joints, one with epoxy resin as a filling material and the other in the dried condition without epoxy resin. The joints were then exposed to monotonic and cyclic loading [5; 6]. In another study, an experimental specimen with a full-depth male-female shear key shape was prepared to analyze the performance of the single epoxy-filled shear key, while considering the fatigue, watertight properties, and temperature of the joint. In addition, static response modeling of the joint was performed through finite element method (FEM) analysis [7]. Various reinforcement shapes and types as well as various lapped splice constructions, including those using U-bars, were used as variables in the evaluation of the structural performance [3; 8; 9; 10]. In addition, strength tests on connection systems were performed using the flange combinations of the Bulb-Tee girder, with analysis of crack propagation and system strength [11]. To verify the tensile performance of the joint, a U-bar was assembled, high-performance concrete (HPC) was cast, and different curing periods were applied [12]. In another study, a 144 MPa ultra-high-performance concrete (UHPC) and a pre-stressing force were introduced to evaluate deflection, shear strength, and tensile performance [13].  
To verify and predict the serviceability, the effective moment of inertia was analyzed and proposed for precast concrete members with joints through the experiment result of deflection of the precast concrete beam with joint in cyclic loading [14].  
As shown in the aforementioned discussion, various studies on the connection method, shape, and performance of joints in structures assembled from precast concrete have been conducted. However, each study only verified the structural stability performance. Consequently, there is an insufficient understanding of the influence of the joints on the deflection of the structure. Thus, the deflection is predicted and compared to experimental values through a static behavior analysis of precast concrete beam joints in this study.