Evaluation of modal contribution to the wind-induced responses of tall buildings

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The frequency domain analysis of structures requires the computation of the frequency response functions (FRF) matrix. Obtaining the FRF matrix is a time-consuming procedure, especially for the structures having large number of degrees of freedom (DOF). For the lightly damped structures, the FRF matrix can be estimated by the superposition of the structure’s dominant modes. In the present study, the modal dominancy analysis is carried out on the wind-induced responses of tall buildings using the frequency domain modal decomposition method. Two examples of tall structures, including a tall building and a tall TV tower are presented. It is found that the wind-induced dynamic displacement response is dominated by the first vibration mode and the effect of the higher modes can be neglected. For the acceleration response, contribution of the higher modes is observed. However, due to low-frequency content of the wind force spectrum, the first mode has the highest effect on the acceleration response. It is also demonstrated that the modal superposition method with contribution of the dominant modes can significantly reduce the order of the FRF matrix and the computing time.