Study of the dynamic response of a three-story frame-type module subjected to two sources of excitation in resonant states

Abstract

The present work examines the dynamic response of a three-story frame-type module subjected to harmonic loads from two unbalanced mass excitation sources. For this purpose, the modal parameters and their velocity response of each floor are analyzed and calculated. The Operational Modal Analysis (OMA) method has been used to identify the modal parameters of the module, namely the natural frequencies of 9.32 Hz, 16.39 Hz, and 28.45 Hz, along with their modal shapes and modal damping ratios of 0.044%, 0.033%, and 0.027%, respectively. The measurement of the dynamic response was performed under resonance conditions with a frequency ratio of 1.15, using the AXL-ACC-16G accelerometers, which integrate the LIS2DH12 sensor, installed on each floor according to the 3² factorial design, which consists of 2 excitation sources where the selected study factors correspond to the operating frequency of the 1st and 2nd motor, and the levels of 10.72 Hz, 18.85 Hz, and 32.72 Hz, for both factors. The experimental data for the factorial design corresponds to the global RMS velocity, that is, the maximum velocity recorded across the three floors, obtained from the acceleration records processed with the VibrationData software. It was determined that the critical condition occurs when both motors operate at 18.85 Hz. This demonstrates the dangerous effect of operating at frequencies close to the normal torsional vibration mode in the case analyzed here.