Application of passive dampers to timber structures is increasing with the aim of reducing seismic response including translation and torsion. The structure in such a case possesses the so-called non-proportional damping. In this paper, new system identification method considering non-proportional damping is proposed. Modal shapes including phase differences of each point are evaluated using special technique, which makes real-valued expression possible. Accuracy of the method is confirmed by comparison with shaking table test. It showed close agreement.
