A practical approach for estimating the floor deformability in existing RC buildings: evaluation of the effects in the structural response and seismic fragility

A study is presented on the evaluation of the floor deformability in the existing RC buildings and the related effects on the structural behaviour and the seismic fragility are investigated. In particular, the study of the seismic behaviour of existing RC buildings is strictly related to the initial assumptions made by practitioners on the numerical model, which usually assume the floor as rigid, according to a criterion of reducing time and computational efforts. Nevertheless, this hypothesis can provide unrealistic responses, with effect of obtaining not conservative results in the vulnerability estimation. In a view of practitioners’ necessities, a new numerical practical procedure is developed, in order to provide an a priori definition about the effective floor deformability of three-dimensional finite element models. This procedure has been tested on a couple of real existing RC school buildings, modelled with several numerical configurations and accounting for the presence of all elements that constitute the entire buildings (floor system, infill panels and elements of retrofit). Based on the evaluation of structural response and seismic fragility, some interesting observations have been provided, with the aim to define and to prevent the possible errors by assuming the floor as rigid.