A New Method For Estimating the Input-Energy of Mdof Structures

Inputenergy is the amount of energy that is imposed by an earthquake on a structure and its correlation with structural damage has been studied and demonstrated by many researchers. since studies concerning seismic energy in multidegreeoffreedom systems are relatively limited compared with single-degree-of-freedom, in this paper, firstly a theoretical exact method is discussed to calculate the inputenergy of the multi-degree-of-freedom elastic oscillators. it is proved that unlike the general rule in mechanics, the superposition theorem is valid for input-energy in conventional modal analysis. to estimate the input-energy, an approach based on phsa to predict the fourier amplitude spectrum, is proposed. the results indicate that the modal mass ratio is not the only decisive parameter in input-energy. modal input-energy decomposition also confirms the possibility of greater input-energy of higher modes in comparison with fundamental ones or the ones with the higher mass participation ratio, especially for tall buildings located in the nearfield seismic zones.