MODAL IDENTIFICATION OF A HEAVILY DAMAGED NINE-STORY STEEL-REINFORCED CONCRETE BUILDING BY AMBIENT VIBRATION MEASUREMENTS

Abstract

Modal parameters of a nine-story steel-reinforced concrete building damaged heavily by the 2011 off the Pacific coast of Tohoku Earthquake were identified from ambient vibration data using frequency domain decomposition (FDD). The characteristics of the identified three-dimensional mode shapes, torsional component of the mode and deformation ratio of the mode were discussed with respect to the seismic damages. In addition, we identified the mode shapes by two kinds of FDD: one for a general viscous damping system, and the other for a proportional damping system. The influence of a viscous damping condition on the identified mode shapes was discussed.