Identification of Modal Parameters of Classically Damped Linear Structures under Multi-Component Earthquake Loading

A new method for the identification of dominant modal parameters (natural frequencies, damping ratios and participation factors) of classically damped linear structures using response to a multi-component earthquake is presented. If different components of the base acceleration of a structure are measured, the possibility of coupling between each of the six components of an earthquake and the measured absolute acceleration of the structure can be investigated. After introduction of the modal equations of motion of classically damped linear systems under multi-component earthquake, a newly proposed method for identification of the structural modal parameters is explained and, by application of the method to a model and on a real structure using artificial and real earthquake records, the accuracy of the method has been verified. The results of this verification indicate that the effect of the multi-input can be important for the identification of modal damping ratios and modal participation factors, and can improve compatibility between the recorded acceleration response and the calculated model response.