In the earthquake response analysis of an elastic multi-degree-of-freedom structure

the mode-superposition response spectrum method can be applied. It is necessary to select an appropriate number of vibration modes in order to obtain satisfactory results with reduced computational work.The number of vibration modes to be included depends on the modal contribution to the total response of the structure due to earthquake excitation.By mathematical derivation

the problems of modal contribution and computational method on the reasonable mode number are analyzed and studied.First

the properties of modal participation factor are discussed.The mathematical expressions of several parameters for structural modal contribution are given and the mechanical meanings are interpreted by theoretical proof.Further

computation methods on the reasonable mode number including effective modal mass method and modal displacement control method are evaluated and compared with each other.This research can provide a theoretical basis and reference for further understanding the structural modal contribution and selecting the reasonable mode number for the earthquake response analysis of structures.