Influence of infill distribution and design typology on seismic performance of low- and mid-rise RC buildings

During last decades, post-earthquake damage (e.g., L'Aquila 2009, Lorca 2011) numerical and experimental studies showed that a growing attention should be addressed to the influence of infills on the seismic performance of Reinforced Concrete (RC) buildings. In this paper, a numerical investigation on the influence of infills on the seismic behavior of RC structures is carried out. Four different case study buildings are analyzed: four- and eightstorey buildings, designed for seismic loads and for gravity loads only. Seismic capacity at two Limit States (Damage Limitation and Near Collapse) is assessed through static push-over analyses, within the N2 spectral assessment framework, and different infill configurations are considered (Bare, Uniformly Infilled, Pilotis). A comparison between IN2 curves related to the different structures is carried out, in order to evaluate seismic response, depending on the number of storeys, the design typology and the infill configuration. Then, fragility curves at both Limit States are obtained, through the application of a Response Surface Method. Seismic performance is also expressed in terms of failure probability, given a reference time period. Moreover, a comparison between fragility analysis results and observed damage during L’Aquila earthquake is carried out, in particular at Damage Limitation Limit State.