Improved dynamic correction method in seismic analysis of both classically and non-classically damped structures

A step-by-step approximate procedure taking into consideration high-frequency modes, usually neglected in the modal analysis of both classically and non-classically damped structures, is presented. This procedure can be considered as an extension of traditional modal correction methods, like the modeacceleration method and the dynamic correction method, which are very eective for structural systems subjected to forcing functions described by analytical laws. The proposed procedure, herein called improved dynamic correction method, requires two steps. In the rst step, the number of dierential equations of motion are reduced and consequently solved by using the rst few undamped mode-shapes. In the second step, the errors due to modal truncation are reduced by correcting the dynamic response and solving a new set of dierential equations, formally similar to the original dierential equations of motion. The dierence between the two groups of dierential equations lies in the forcing vector, which is evaluated in such a way as to correct the eects of modal truncation on applied loads.