A DAMAGE-BASED DEFINITION OF EFFECTIVE PEAK ACCELERATION

This paper presents a rational basis for obtaining the Effective Peak Acceleration (EPA) of a given ground motion process. The proposed form ulation considers the statistical variability in the ground motion, an d is centred on the idea of explicitly linking EPA with expected cumul ative damage in the structures due to the inelastic excursions. The st ructural behaviour has been modelled by a Single-Degree-of-Freedom (SD OF) bilinear hysteretic oscillator. EPA is considered to be the expect ed PGA of a scaled ground motion process such that this oscillator und ergoes a specified expected damage under the unsealed process if it is linearly designed for the scaled process. For estimation of the damag e, the oscillator has been replaced by an equivalent linear oscillator through stochastic averaging. A parametric study has been carried out to investigate the dependence of EPA on several governing parameters, and it has been shown that despite the strong dependence of EPA on os cillator time period, it may be possible to obtain 'period-averaged' E PA values for several ground motion processes for engineering applicat ions. (C) 1998 John Wiley & Sons, Ltd.