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This study presents a comprehensive investigation into the dynamic response of a multi-story building equipped with a Tuned Mass Damper (TMD) system under seismic excitation. The research focuses on evaluating the effectiveness of passive TMDs in mitigating structural vibrations, while accounting for changes in structural properties due to damage.

The adopted methodology is based on numerical modeling of a multi-degree-of-freedom (MDOF) system subjected to a broadband synthetic ground motion with a peak ground acceleration (PGA) of 0.30g. Modal analysis was first performed to determine the fundamental dynamic characteristics of the structure. Subsequently, Frequency Response Function (FRF) analysis was conducted to assess the structural behavior with and without TMD systems. Different TMD mass ratios (0.5%, 1%, and 2%) were examined to evaluate their influence on vibration control performance. To simulate realistic conditions, both global and localized damage scenarios were introduced through stiffness reduction, allowing for the investigation of frequency shifts and their impact on system efficiency.

The results indicate that TMD systems are highly effective in reducing structural response in the undamaged condition, particularly when properly tuned to the fundamental frequency. The introduction of the TMD significantly decreases resonance peaks and redistributes vibrational energy. Increasing the mass ratio improves performance, with the 2% TMD achieving the highest level of response reduction. However, as structural damage increases, a noticeable reduction in natural frequency is observed, leading to detuning between the TMD and the primary structure. This detuning results in a progressive decline in TMD effectiveness, especially at higher damage levels. Additionally, the findings reveal that damage in lower stories has a greater impact on overall system behavior compared to damage in upper stories. Despite these challenges, the TMD system remains effective in reducing inter-story drift, thereby enhancing structural safety.