This study investigates the seismic response of reinforced concrete buildings designed according to the current Italian building code. Number of stories, site hazard, presence and distribution of masonry infill panels, and type of lateral resisting system are the key investigated parameters. The main issues related to design and modeling are discussed. Two Limit States are considered, namely Global Collapse and Usability-Preventing Damage. The main aim of the study is a comparison between the seismic response of the buildings, investigated through nonlinear static and dynamic analyses. Irregularity in the distribution of infill panels and site hazard emerge as the most influential parameters.

The prediction of the seismic response of structures requires accurate models for describing the behavior of each structural element. In frame analysis, non-linearities are typically modeled through either lumped or distributed plasticity elements. Another important assumption is needed for the selection of the appropriate section model. Phenomenological laws for the section behavior are computationally faster but less accurate than fiber-section models. This study compares the predictions obtained for reinforced concrete sections and simple single columns with a phenomenological section law (combined with a lumped plasticity element) and with a fiber-section model (combined with a distributed plasticity element). The phenomenological section model is that proposed by Ibarra et al. (2005) with the predictive equations used by Haselton et al. (2008). The fiber section distributed element is that by Spacone et al. (1996a,b). Comparisons show some important differences in the section responses (particularly for high levels of axial load) and in predicting the responses of experimentally tested columns.

This paper presents a study on the selection of engineering demand parameters (EDPs) for the definition of collapse for code-conforming reinforced concrete buildings. The definition of collapse for buildings is not unique, as different codes and authors define it with respect to different EDPs and different values of the EDPs. Since collapse is associated with large plastic deformations, collapse is typically defined by deformation, displacement, and eventually energy EDPs. The EDPs can be either local when they refer to a single structural element response parameter (such as element rotation with respect to the chord) or global when they refer to an overall building response parameter (such as inter-story drift or top floor displacement). The Italian buildings code NTC2008 and Eurocode 8 use the chord rotation as EDP, while FEMA 356 and other North American literature use inter-story drift ratio. This study compares different definitions of EDPs and different values of the selected EDPs by analyzing two code-conforming benchmark buildings, one six-story and the other nine-story high, designed according to Italian code. Multiple-stripe, non-linear dynamic analyses are carried out on the two buildings modeled with concentrated hinges. The results show that different collapse definitions lead to very different safety evaluations and point to the need for the definition of a single EDP and a single value to make collapse analyses (and risk assessment) studies comparable.