THE APPLICATION OF THE SPECTRUM METHOD FOR THE EVALUATION OF NON-LINEAR RESPONSE OF STRUCTURES SUBJECTED TO EARTHQUAKE GROUND MOTIONS

摘要

It is common practice to define the non-linear response of the structures subjected to earthquake ground motion by using the Newmark inelastic spectra, for which the linear free field spectra are modified by employing the ductility of structural materials. The least of the problems, which arises by the application of such approaches, are that, no allowance has been accounted for the amplitude dependency of the frequency and, thus, this will lead to an unrealistic evaluation of the response of the structure as the frequency of a non-linear system will be reduced by increasing the amplitude of the system and the ductility factor. This is particularly important for the evaluation of the displacement response of structures, as generally more flexibility results in more deflection. This paper addresses the problem and presents a practical method using the spectrum approach, in which the amplitude dependency of the frequency is considered. A comparison between the results of this method and those from the full non-linear analysis indicates a good correlation between the results of the two methods through the whole range of frequencies particularly for the displacement response of the structures.