Formulation of performance levels and relevant limitations for clay brick masonry infills in seismic analysis of R/C frame structures

Observation of damage caused by recent earthquakes highlights, once again, that the presence of infills significantly affects the seismic response of reinforced concrete (R.C.) frame buildings. Therefore, in spite of the fact that infills are non-structural elements, and thus they are normally not considered in structural analyses, in many cases their contribution should not be neglected. Based on these observations, the study proposed in this paper consists in the evaluation of the seismic response of infills in time-history finite element analyses of R.C. frame structures by means of a two-element model, constituted by two diagonal nonlinear beams. A “concrete”-type hysteretic model predicts the in-plane state of infills, through a force-displacement backbone curve expressly generated, and scanned in terms of performance limits, to this aim. This model is demonstratively applied to a real case study, i.e. a R.C. frame building including various types of brick masonry perimeter infills and internal partitions, damaged by the 30 October 2016 Central Italy earthquake. The time-histories seismic analyses carried out on it allows checking the influence of infills on the response of the structure, as well the effectiveness of the proposed model in reproducing the observed real damage on the masonry panels.