The main motivation of current study is to present the results of an investigation conducted to obtain a relationship between damage index/damage level and residual displacement. SDOF systems with known lateral strength for periods ranging from 0.1 to 3.0 seconds are investigated for this purpose. Two hysteretic behaviours consisting of elastoplastic (non-degrading) and Modified Clough (degrading) models are assumed during analyses. A total of 140 ground motions including both far-field and near-field ground motions are considered in nonlinear dynamic time history analyses. A new damage index is proposed in terms of residual displacement, spectral displacement, maximum inelastic displacement and lateral strength. The comparison of proposed damage index with the analysis results is also presented.
