Inelastic displacement ratios for design of structures with constant damage performance

This paper summarizes the comprehensive statistical results of constant damage inelastic displacement ratios which allow the evaluation of maximum inelastic displacement demand for structures with constant damage performance. The inelastic displacement ratios are calculated with modified Park-Ang damage index and inelastic single-degree-of-freedom systems subjected to 573 ground motions. The influences of period of vibration, levels of damage, site conditions, earthquake magnitude, rupture distance, post-yield stiffness, stiffness degradation, strength deterioration, parameter β and ultimate ductility factor μu in damage index model are evaluated and discussed statistically. It is found that the effect of site conditions is not very significant. Specifically, coefficients of variation are approximately period-independent and site-independent. The degrading systems with short period of vibration would experience larger inelastic displacement than non-degrading systems. The effects of parameter β and ultimate ductility factor μu are moderate in short period region. A simplified expression is proposed for the application of constant damage inelastic displacement ratios.