The structural health monitoring (SHM) system to evaluate the drift angle by measuring the plastic heat generation of steel materials was proposed. In this study, the steel slit damper (SSD) is considered as a heat-generating member. However, SSDs are susceptible to failure under cyclic loading due to crack formation. A pre-twisted steel body (PTS) is proposed in this study, designed to act as a steel slit damper (SSD) by utilizing its pre-twisted slit section for energy dissipation. Static cyclic loading tests were conducted, taking the twist angle of the slit section as the variable. The experimental results show that the twist angle of the pre-twisted slit section progresses with loading, leading to a gradual decrease in the PTS's loading capacity and stiffness. This indicates that the twist angle of the pre-twisted slit section influences the mechanical behavior and restoring force characteristics of PTS. Moreover, an appropriate pre-twisted deformation significantly improves the cumulative deformation capacity of the specimen. Based on experimental results, a theoretical equation for the mechanical characteristics of PTS is proposed and validated.