Comparison of Peak Ductility Demand of Inelastic SDOF Systems in Maximum Elastic Response and Major Principal Directions

Abstract

This study investigates the orientation dependency of the peak ductility demand of inelastic single-degree-of-freedom (SDOF) systems of known strengths by taking the record-to-record variability of seismic effects into account. The probabilistic characteristics of the peak ductility demand in recording directions on the horizontal plane are compared with those in the maximum elastic response direction and the major principal direction. The analysis results indicate that the peak ductility demand depends on how input ground motions are defined in terms of record orientation. The observed orientation dependency can be explained by noting the response spectral shapes of scaled ground motion records in specific directions. The results have important implications for current earthquake engineering practice, suggesting that separate peak ductility demand models should be used for different ground motion directions to evaluate the seismic performance of structures consistently and without bias.