## 1 Introduction  
Reinforced concrete (RC) structures experience degradation throughout their lifespan. Notably, structures without seismic design require seismic retrofitting. To address these issues, various retrofit techniques have been explored and implemented. The retrofitting of RC structures primarily targets columns and beams, with each possessing unique retrofit requirements dictated by their functional roles and characteristics. Columns play a crucial role in dissipating energy during seismic events. To enhance this capability, strategies such as integration of dampers, enlargement of cross-sections, and bracing have been employed to resist seismic load [1; 2; 3]. The RC beam primarily serves as a material resistant to bending. Therefore, the retrofitting strategy for beams is focused on enhancing their flexural capacity. In this context, fiber-reinforced polymers (FRP) and steel plates have been widely adopted [4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20]. Additionally, one widely used method for retrofitting beams is utilizing fiber-reinforced materials such as ultra-high-performance concrete [16; 17; 18; 19; 20]. [PERSON] et al. [16] and [PERSON] [17] conducted a comprehensive review focusing on recent advancements in evaluating the efficacy of reinforced concrete (RC) structures enhanced with engineered cementitious composite (ECC). ECC exhibits notable properties such as tensile strain hardening behavior and robust interfacial bonding capabilities with substrate concrete, rendering it a viable candidate for retrofitting applications. This review showed that employing ECC for strengthening purposes significantly enhances the structural performance of RC systems. The investigation conducted by [PERSON] et al. [18] examined reinforced concrete beams retrofitted using either ultra-high-performance concrete (UHPC) or carbon fiber-reinforced polymer (CFRP). Their findings revealed that UHPC exhibits superior toughness, displacement capacity, and fracture energy compared to CFRP retrofitting. Consequently, UHPC emerges as a favorable option for strengthening reinforced concrete structures, offering both technical advantages and economic benefits. Additionally, [PERSON] [19] and [PERSON] [20] delved into a retrofitting approach utilizing carbon nanotubes (CNTs). Their studies demonstrated that CNTs effectively fills voids within the concrete matrix, resulting in a notable enhancement in compressive strength. [PERSON] proposed a cost-effective method for repairing damage in the existing frame structure with enhanced strength and ductility [21]. However, retrofitting RC beams presents challenges, such as limited workspace availability and the use of heavy retrofit materials. Although FRP can mitigate some of these issues by employing strips, its inherent material properties may cause brittle failures [10]. Both steel plate and FRP methods are prone to debonding issues with RC components [22; 23]. Cracks in RC beams can be observed before the full potential of steel plates or FRP is realized, leading to debonding and compromised structural integrity. Recent studies [24; 25] introduced an innovative retrofitting approach for RC beams using modularized steel plates, bypassing the constraints of traditional RC beams retrofitted with FRP and steel plates. This novel method presents benefits including weight, construction ease, and adaptability to various beam sizes. Importantly, it effectively overcomes debonding issues and enhances the structural performance of the existing RC beam by approximately 1.8 times [25]. However, in this new method, the modularized steel plates were not bonded to each other, and integration with the RC beam relied solely on chemical anchors. Experimental results from previous research [24; 25] confirmed that when the RC beam experiences bending moments, gaps occur between the modularized steel plates.