Damage-Based Inelastic Seismic Spectra

Current inelastic seismic spectra suffer from a conceptual limitation: they are significant only on the maximum demand of ductility and they do not include any influence of the number of response cycles, yield excursions, stiffness and strength degradation and damage potential to structures. This paper presents a stochastic approach for obtaining damage-based inelastic seismic spectra. In order to consider the cumulative damage phenomenon in structural systems under strong ground motions, the authors adopt the Park and Ang damage model that includes the displacement ductility and the hysteretic energy. The novelty is that the peak theory of random processes is adopted to achieve damage-based seismic spectra. This approach has some advantages compared with the standard statistical approaches based on a large number of recorded accelerograms. First, it drastically reduces the computational effort, while allowing us to typify the seismic motion by some parameters such as the frequency content, peak acceleration, energy content and strong motion duration, i.e. all the parameters that affect the structural response under seismic actions. Besides, it allows to obtain the following stochastic inelastic seismic response spectra: damage-based (i) displacement and acceleration inelastic spectra, (ii) response modification factor spectra, (iii) yield strength demand spectra, and (iv) damage-based inelastic displacement ratio spectra.