# Structural Performance of a Precast Concrete Modular Beam Using Bolted Connecting Plates
## 3 Experimental Program  
### Specim Details  
One of the primary issues for PC beams is how to resist shear forces rather than flexural capacity since PC is used in structures with a large cross-section in general. Therefore, while only the flexural test was conducted in the previous study [20], this study also investigated shear behavior. This paper considered that the splicing performance of the proposed method was sufficient if the PC modular beams showed a similar structural performance to that of a monolithic RC beam. Therefore, two RC beams and two PC modular beams were manufactured to evaluate structural performance. The notation of specimens is shown in Figure 4. The MCF and PCF specimens for the flexural tests were 300 mm in width and 350 mm in height with span lengths of 4500 mm. The reinforcement detail was designed according to the Korean Design Standard (KDS 14 20 50:2018) [21]. When conducting the flexural test, stirrups with a diameter of 10 mm were arranged at 150 mm spacings to prevent shear failure of the beams. The MCS and PCS specimens for the shears test had the same section as the specimens for the flexural test and span lengths of 2400 mm. Six rebars with a diameter of 22 mm were used to prevent flexural failure before shear failure. Based on the midspan, both modules are designed to have the same amount of steel plate as the steel reinforcement. The upper connecting plate and the lower connecting plate had the same amount of compressive reinforcement and tensile reinforcement. The size of the connecting plate depended on the amount of steel reinforcement. The thickness of the connecting plate was 5 mm, which is the most widely used, and the length was 800 mm for the flexural test specimen and 400 mm for the shear test specimen. The embedment length of the connecting plates was determined as provided in KDS 14 20 52:2021 [22] due to the prevention of pull-out failure. It is specified that the embedment length should be at least 150 mm in KDS 14 20 52: 2021 [22]; thus, the embedment length of the connecting plates in PCF and PCS were 300 and 150 mm, respectively. Drawings of the specimens are presented in Figure 5. The material properties were measured according to Korean standards [23; 24; 25]. The compressive strength of concrete was measured according to KS F 2405 [23], the compressive strength of non-shrink mortar was measured according to KS L 5105 [24], and the yield strength of rebars and steel for connecting plates were measured according to KS B 0802 [25]. Korean standards specify that the material properties can be determined from the average of the test results of three or more specimens; thus, this study manufactured three specimens for every material, and their properties were evaluated. The details of specimens are summarized in Table 2. The material properties in Table 2 are mean values. Figure 6 shows the procedure used to construct the PC modular beams. As shown in Figure 6a, PC modules were transported to the site and the U-shaped plate and I-shaped plate were connected by bolting as shown in Figure 6b. After the connection of the plates, non-shrink mortar was injected into the connection region as shown in Figure 6c. Before injecting non-shrink mortar, concrete chipping was employed in order to increase adherence to smooth surfaces. The form was removed when the compressive strength of the non-shrink mortar had reached the design compressive strength, 60 MPa, as confirmed by a uniaxial compression test.  
Figure 3: Construction process of the proposed precast concrete modular beam system: (**a**) connection between U-shaped and I-shaped steel plates; (**b**) bolted connection between plates; (**c**) injection of non-shrink mortar.  
Figure 4: Notation of specimens.  
Figure 5: Drawings of the specimens for flexural and shear tests (mm): (**a**) monolithic specimens; (**b**) PC modular specimens; (**c**) sideview of monolithic beam specimens; (**d**) sideview of precast concrete modular specimens; (**e**) A-A section; (**f**) B-B section.