## 3 Experimental Program  
### Specimen Details  
In this study, the seismic performance of reinforced concrete columns retrofitted with RSL was evaluated to assess the role of RSL as a structural fuse. The cyclic loading tests were conducted on five test specimens of reinforced concrete columns retrofitted with RSL. To investigate the behavior of the RSL-retrofitted specimens in both stage 1 and stage 2, the length of the sliding slot was varied. Additionally, to examine the behavior of retrofitted specimens under a torsional load, which occurs during real earthquakes, the magnitude of the torsion was altered by changing the eccentric distance of the lateral force applied to the specimens. The eccentricity distance refers to the distance offset from the centerline of the column. Considering the experimental conditions designed to induce maximum bending and torsion in the column, the eccentric distance was determined to be larger than the core  
Figure 3: Behavior of the RSL system: (**a**) stage 1 and (**b**) stage 2.  
section of the column, measuring 62.5 mm [19; 20]. Therefore, the eccentric distance was set at 65 mm. Additionally, to investigate the influence of torsion, an eccentric distance of 130 mm, twice the value of 65 mm, was also adopted. The experimental variables are listed in Table 1. A previous study [18] examined the seismic performance of RSL compared to non-retrofitted concrete columns. This study specifically concentrates on evaluating the torsional behavior of RSL-retrofitted specimens, an aspect that has already been validated in previous studies and assessing the replaceability of the steel link after a seismic event. Therefore, it is important to note that non-retrofitted concrete column specimens were not used as a control specimen in this study. The determination of the sliding slot length was grounded in the initiation points of flexural and shear cracks in reinforced concrete columns, as identified in previous research [18] through cyclic loading testing. In conceptual terms, a sliding slot length of 5 mm indicates that the steel link begins to resist loads following the occurrence of flexural cracks in the reinforced concrete column. On the other hand, a sliding slot length of 10 mm implies that resistance initiation takes place after the development of shear cracks. Figure 4 is intended to introduce the notation of specimens. The test specimens consisted of a reinforced concrete column, a foundation, and the RSL. The column had a square cross-section, with each side measuring 250 mm and a height of 2050 mm. The top 250 mm of the column was allocated for the application of lateral forces. The foundation, designed for the installation of the RSL and to secure the specimen, measured 1400 mm in width, 425 mm in height, and 1270 mm in length. All specimens were designed following the guidelines of ACI 318-19 [21], ensuring that the design was consistent with the non-seismic detailing of reinforced concrete columns. The longitudinal reinforcement was four deformed bars with a diameter of 22 mm and a yield strength of 400 MPa. Stirrups were made of deformed bars with a diameter of 10 mm and a yield strength of 400 MPa, spaced at 125 mm, which is half the minimum column dimension of 250 mm. The columns were cast using concrete with a compressive strength of 24 MPa, while the foundation was made of concrete with a compressive strength of 30 MPa to prevent premature failure. The material properties of the specimens were determined through experimentation, and the average values of three specimens were considered. The