Impact of masonry infill variability on the estimation of floor response spectra in RC buildings

Although the seismic performance of non-structural elements is currently recognised as a key issue in the seismic behaviour and loss estimation of buildings, both at the individual and portfolio level, the accurate evaluation of the seismic demand to which the former are subjected is still an open issue. Code formulations, as well as simplified methodologies for regional scale applications, are often based on inaccurate distributions of peak floor accelerations and floor spectral accelerations. In this respect, one of the main shortcomings in the formulations available in the literature is related to the effect of masonry infills on Floor Response Spectra (FRS), which is generally neglected, even in recently proposed design/assessment-oriented simplified methodologies. This study highlights and quantifies the impact of different masonry infill typologies on FRS estimates in existing infilled reinforced concrete (RC) frames. Nonlinear time history analyses are carried out for different case-study RC frames, selected from a fully integrated building portfolio, representative of buildings designed according to the Italian codes in force between 1970 and 1980. To account for the infill-related uncertainty, a macro-level distinction of common infill types, in terms of shear strength, was used. Moreover, the influence of the geometrical configuration and the number of storeys was also investigated. Acceleration FRS were then computed and statistically characterised, based on the observed infill-to-infill-related variability.