###### Abstract  
This study focused on perforated bricks, and the structural performance enhancement of brick members by internal reinforcement was experimentally investigated. As a new reinforcing material, screw iron (SI) rods were selected for the internal reinforcement, and they were inserted into the perforated brick. To investigate the most-effective reinforcing method as well as to understand the fundamental structural behaviors, four specimens with different variables were fabricated, and three-point bending tests were carried out. From the experiments, it was found that the maximum strength of the specimen increased by more than two times with internal reinforcement. The internal reinforcement, fixed by nuts at both ends of the specimen to enhance integrity, increased the maximum strength by nine times. Moreover, the deformation capacities of the specimens were also greatly enhanced. The case where the internal SI rods were fixed by nuts without mortar also showed a similar structural performance to the case with mortar. The estimation methods of the maximum strength of the specimens were also discussed, and they showed reasonable agreement with the test results. It was proved that the proposed material and methods enabled effective utilization of the internal reinforcement, and they could contribute to the improvement of structural performances in masonry construction.  
e 2023 1  
In order to improve the seismic capacity of URM structures, reinforcing or retrofitting methods were developed, and the seismic performances of reinforced masonry (RM) members against in-plane and out-of-plane loadings were evaluated by previous studies [25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46]. Some of them used new materials with steel fiber or waste marble powder [25; 26]. Many of them employed outer-surface reinforcing or retrofitting schemes by using ferrocement, reinforced plaster, shotcrete, fiber-reinforced polymers [27; 28; 29; 30; 31; 32; 33; 34], etc. In a few cases, reinforcing methods by internal steel reinforcement were conducted for masonry members [35; 36; 37; 38]. They were usually for the CB units with relatively large holes, and some focused on the reinforcement of the bed joint mortar. Prestressing techniques by post-tensioning forces were also applied to the masonry members [35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46], and some reinforcing schemes were introduced in the design codes and guidelines [47; 48]. The prestressing forces were provided by external or internal tendons such as high-strength strands and steel bars. On the other hand, such post-tensioning skill is somewhat difficult to apply to small structures and increases the construction cost. Measuring or managing the tension stress of tendons would also be complicated.  
Especially for the brick member, it has been common practice to apply reinforcing materials to the outer surface, and there were few attempts focused on internal reinforcing. Moreover, the structural performances of out-of-plane behaviors were less considered. Hence, in the previous study by the authors of [49], the deformed reinforcing bars were arranged inside the perforated bricks, supposing the brick silt member mentioned earlier, and their structural performances, in the out-of-plane direction, were experimentally investigated. Although the enhancement in structural performance was obtained to some extent, it was found that the reinforcing effect could be drastically decreased when the bond action and integrity between the internal bars and mortar was poor, which was indicated as an important future task. Therefore, in this study, a crucial improvement was made to enhance those defects between internal reinforcement and mortar by using new reinforcing materials and methods, and its effectiveness was verified based on experimental discussions, which could provide more robust stilts and brick members.