SUMMARYIn many parts of the world, the repetition of medium-strong intensity earthquake ground motions at brief intervals of time has been observed. The new design philosophies for buildings in seismic areas are based on multi-level design approaches, which take into account more than a single damageability limit state. According to these approaches, a sequence of seismic actions may produce important consequences on the structural safety. In this paper, the e ects of repeated earthquake ground motions on the response of single-degree-of-freedom systems (SDOF) with non-linear behaviour are analysed. A comparison is performed with the e ect of a single seismic event on the originally non-damaged system for di erent hysteretic models in terms of pseudo-acceleration response spectra, behaviour factor q and damage parameters. The elastic-perfect plastic system is the most vulnerable one under repeated earthquake ground motions and is characterized by a strong reduction of the q-factor. A moment resisting steel frame is analysed as well, showing a reduction of the q-factor under repeated earthquake ground motions even larger than that of an equivalent SDOF system.

No abstract

SUMMARYThe aim of the paper is to explore the possibilities offered by SAP2000 ® v.10, a software package with user-friendly interface widely used by practising engineers, for seismic analyses of masonry buildings. The reliability of the code was first investigated by carrying out static push-over (SPO) analyses of two walls, already analysed by other researchers using advanced programs. The equivalent frame modelling was employed in all analyses carried out. The code was then used to investigate the seismic performance of an existing two-storey building typical of the north-east of Italy, with the walls being made of roughly squared stones. An SPO analysis was performed first on the most significant wall, followed by a number of time-history analyses aimed to evaluate the dynamic push-over curves. Finally, the seismic fragility curves were derived, considering the seismic input as a random variable.

No abstract