# Structural Performance of a Precast Concrete Modular Beam Using Bolted Connecting Plates
## 5 Conclusions  
This paper proposed a PC modular system using bolted connecting plates to replace the grouted splice sleeves used in typical PC modules and simplify the construction process. To evaluate structural performance, monolithic RC beam and PC beam specimens were manufactured, and flexural and shear tests were conducted. The main conclusions of the study are as follows:  
1. The flexural test indicated that initial flexural cracks occurred in the midspan of both the monolithic RC beam (MCF specimen) and the PC beam with a bolted connecting plate (PCF specimen). In the shear test, the shear cracks extended from the support to the loading point. In every PC modular specimen, cracks developed at the bottom of the connection as the load increased, and these cracks propagated along with the connection to the compression zone and failure occurred. The connection between the PC modules ensured splicing performance until the experiment was terminated, and brittle failure was not observed;
2. The maximum flexural and shear strengths of the PC modular beam using a bolted connecting plate were 88.3% and 88.8% of those of the monolithic RC beam, respectively. PC modular beam specimens ensured splicing performance because there was no region where the stiffness was decreased until reaching the maximum load, and the load decreased gently after reaching the maximum load;
3. The flexural test indicated that the rebars of the MCF and PCF showed similar strain distributions as the load increased and exceeded yield strain near the maximum load. It was indicated that the rebar effectively resisted tensile stress. The bolted connecting plate inserted into the PC module exceeded the yield strain of 0.00138. The results of the shear test confirmed that the strain of the stirrup located closer to the loading point increased dramatically as with the RC monolithic beam. Therefore, the bolted connecting plate can transfer stress to each PC module effectively, showing excellent splicing performance, and it can deal with problems that may occur in typical modular structures;
4. The applicability of ACI 318-19 to the PC modular structure with a bolted connecting plate was evaluated. Experimental results showed that the maximum moment and shear strengths were approximately 101% and 103% of the design moment strength calculated through ACI 318-19. Thus, the proposed PC modular method meets the requirements of the current design code, such as ACI 318-19, and the PC modular beam performed similarly to the general monolithic RC beam. Therefore, the proposed method using a bolted connecting plate ensured splicing performance and had excellent structural performance.  
Conceptualization, K.M.R. and Y.H.L.; methodology, K.M.R.; validation, M.S.K. and C.G.C.; formal analysis, K.M.R.; investigation, M.S.K. and C.G.C.; writing--original draft preparation, K.M.R.; writing--review and editing, Y.H.L. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was supported by a National Research Foundation of Korea Grant (NRF-2019R1A4A1028116), funded by the Ministry of Education, Korea.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data sharing not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.