MODAL ANALYSIS FOR FLEXIBLE BASE ECCENTRIC BUILDINGS

The modal translation and modal rotation are not the same even at elastic state for the systems with the non-classical damping. The 2DOF modal stick based on the 2DOF modal equation has been developed to deal with the seismic analysis of one-way asymmetric fixed base systems and allows the modal rotation to differ from the modal translation. In this paper the applicability of this method in the seismic linear analysis of flexible base asymmetric buildings has been studied. The results show that the efficiency of this modal method using first limited number of modes (usually three fist modes) for the structure response is very good; but for the foundation response seems that it is necessary to consider enough number of modes because of the effects of higher modes of SSI system. Also the results show that generally the estimation of this method for the displacement is better than rotation estimation.