The paper presents a research study concerning some critical issues related to the seismic modelling and analysis of typical existing RC buildings in Southern Italy. When speaking of existing buildings, first important issue is represented by the reliable appraisal of the parameters involved in the structural modelling, such as the concrete mechanical strength. It is evident that a correct assessment is crucial for obtaining an effective structural model in the elastic and inelastic field. Another key point is the choice of the proper method of analysis, since in some cases the standard methods proposed by European Codes are not effective in order to evaluate the structural behaviour of existing buildings. In order to investigate the effects of these aspects on the structural response, extensive comparisons have been performed on different structural models, obtained by properly varying the concrete strength value and by considering also a possible inhomogeneous distribution of the concrete class at different floors. Considering the specific framework of irregular buildings, analyses and consequent discussions have been performed by comparing conventional and multimodal pushover analyses and nonlinear incremental dynamic analyses.
