Dynamic properties are the functions of physical properties. Over the past 20 years, considerable efforts have been made in investigating the relationship between structural damage and modal parameters. Many methods have been introduced ranging from direct methods to application of optimization algorithms. Most of the authors concluded that the dynamic properties are feasible as damage indicators. However, most of the works are validated through analytical models instead of experimental verification. Thus, this study aims to investigate the efficiency of modal curvature and natural frequencies in damage detection through an experimental example of a rectangular hollow section steel beam. Seven damage scenarios are simulated on the specimen using grinder cuts for different damage location and severity. Sensitivity study on the damage index of modal curvature is performed and issues related to the application using modal data are discussed. The results show that natural frequency is a sensitive damage existence indicator. While, the reliability of modal curvature is quite limited and very much depending on the accuracy and precision of measurements.