# Structural Performance of a Precast Concrete Modular Beam Using Bolted Connecting Plates
## 1 Introduction
[PERSON] et el. [13] divided grout sleeves into two types; one was a full grout sleeve, which connected a sleeve and the rebar at both sides, and the other was a half grout sleeve, which is shorter than the full grouting sleeve and connects the sleeve and rebars through a screw thread at one side. Experimental results have shown that precast concrete structures have seismic performances similar to that of a monolithic structure, but there were differences in crack propagation, strain, and deformation of the joints. It has been confirmed that the length of grouting into splice sleeve and length of the cast-in-place region may affect the seismic behavior of a precast concrete structure. Recently, studies have focused on the behavior of precast structures under cyclic loading, because for these types of structures, seismic behavior may be different to that of cast-in-place RC structures [16; 17; 18]. Many studies have confirmed that the structural performance of PC modules connected by grouted splice sleeve is similar to that of monolithic structures. However, if the filling of grout mortar is insufficient, adequate capacity may not be ensured. Therefore, this study proposed a PC modular beam system that can improve on the disadvantages of the rebars' connection method of the existing PC module. This system applies connecting plates, which are mainly used in steel modules, to the PC module to connect the rebars of each module. The main goal of the proposed connection method is to improve the construction difficulty in the existing connection method, which is used splice sleeve and joined horizontally. Table 1 shows a comparison between previous PC modules connected with steel plates and the proposed connection method. The purpose of proposed connection detail is to apply it to PC modular beams. In order to transfer bending and shear stress to module, it is designed considering the behavior of the beam. Figure 1 presents stress distribution in PC beams connected with the proposed method. The stress in one PC module can be transferred to the other PC module via connecting plates. The proposed method has bolted connecting plates: a set of U-shaped and I-shaped plates. The I-shaped plate is inserted into the U-shaped plate and the two plates are connected using bolts. This method can accommodate alignment issues with the steel modules, allowing adjustment for unexpected construction errors. In addition, since the bolted connecting plate replaces rebar in the connection region, splice sleeves are not needed, avoiding problems caused by insufficient grouting on-site. The proposed connection method is for the connection between members where shear force and bending moment are mainly applied. Therefore, a flexural test and a shear test under monotonic load were conducted. Two monolithic reinforced concrete (RC) beam specimens and two PC modular beam specimens were manufactured. This paper assessed the applicability of the proposed PC modular beam to the provisions of American Concrete Institute (ACI 318-19) [19] based on the experimental results.