ABSTRACT
Abstract In this paper a consistent method that considers the low
cycle damage to evaluate the part of the monotonic ductility that the structure can develop under seismic loading is proposed. It is based on the estimation of the number of inelastic cycles and on a statistical characterization of the distribution of plastic excursions; the parameters chosen in the analysis are the fundamental period of the structure, the yielding level, the effective duration of earthquake and a damage structural parameter. Keywords: Seismic-resistant design, Inelastic cycles, Damage
1 Introduction
The first and fundamental step in seismic-resistant design of structures is the reliable evaluation of design forces in relation with the possible ground motions that can occurs in the site of the structure. Currently, it is accepted that the structures can tolerate a certain degree of damage and therefore the design is conducted using a Smoothed Inelastic Design Response Spectra obtained thought the use of a reduction factor R depending on the displacement ductility \i. These inelastic spectra give only the value of the maximum global ductility demand and don't are able to give a reliable definition of the damage potential of the earthquake due to low cycle damage. Some researchers, in fact, have underlined that the real inelastic response of structures is depending on the entire inelastic displacement history (related to the structural damage) and a powerful analytical tool to define the effective required strength can be represented by the damage functionals [Bertero and Uang (1992), Krawinkler and Nassar (1992), Cosenza and Manfredi (1992b)].
