Abstract: To investigate the dynamic response of fusion reactor key system structures and their sites under environmental micro-vibration excitation, a representative key system building of a fusion reactor was selected as the study object. Field measurements were conducted to capture the time-domain responses of both the building structure and the underlying site under environmental and vehicle-induced excitations. Using the power spectral density method and the least squares complex exponential method with multiple reference points, dynamic characteristic parameters were extracted to identify the micro-vibration response characteristics of the structure and site under different excitations. The micro-vibration performance of the structure was then evaluated based on general vibration criteria for sensitive equipment. The results indicate that, under environmental excitation, the peak structural velocity remains below the criterion threshold, demonstrating satisfactory vibration isolation performance. However, under vehicle-induced excitation, large-amplitude vibrations generated by vehicle operations are transmitted through the column bases to the site, resulting in peak ground velocities within the building exceeding the allowable limits. This suggests that the current vibration isolation measures are insufficient, and additional vibration mitigation strategies for sensitive equipment within the structure are necessary.

Key words: steel structure workshop, micro vibration, power spectrum, Polylscf, natural frequency