STATISTICAL INSIGHT INTO CONSTANT-DUCTILITY DESIGN USING A NONSTATIONARY EARTHQUAKE GROUND MOTION MODEL

A recently developed earthquake ground motion model non-stationary in both intensity and frequency content is validated at the inelastic Sin gle-Degree-Of-Freedom (SDOF) structural response level. For the purpos e of this study, the earthquake model is calibrated for two actual ear thquake records. The objective of a constant (or target) displacement ductility used in conventional earthquake-resistant design is examined from the statistical viewpoint using this nonstationary earthquake mo del. The non-linear hysteretic structural behaviour is modelled using several idealized hysteretic SDOF structural models. Ensemble-average inelastic response spectra corresponding to various inelastic SDOF res ponse (or damage) parameters and conditioned on a constant displacemen t ductility response are derived from the two identified stochastic gr ound motion models. The effects of the type of hysteretic behaviour, t he structural parameters, the target displacement ductility factor, an d the ground motion model on the statistics of the inelastic response parameters are thoroughly investigated. The results of this parametric study shed further light on the proper interpretation and use of inel astic response or damage parameters in earthquake-resistant design in order to achieve the desirable objective of 'constant-damage design'. (C) 1997 by John Wiley & Sons, Ltd.