Two frugal options to assess class fragility and seismic safety for low-rise reinforced concrete school buildings in Southern Italy

A study is presented on the seismic fragility of a sample of 15 reinforced-concrete school buildings built between 1960 and 1980s in the province of Foggia, Southern Italy, for which near-perfect information is provided on geometrical and mechanical parameters. In particular, the focus is on the application of two probabilistic methods, employing different compromises in terms of complexity versus accuracy. First, a Eurocode 8 compatible nonlinear static approach is employed, which is augmented via the use of the regression expressions of the SPO2FRAG tool to incorporate record-to-record variability. Second, a nonlinear dynamic approach is used to directly account for record-to-record variability via a constrained multi-stripe analysis. In particular, in view of practitioners’ needs (analysis time, computational efforts, software used), a practical mode for application of the multi-stripe analyses is proposed, based on conducting few stripe analyses, in order to predict the behavior of structures in both the elastic and inelastic ranges of response. Both the static and the dynamic approaches are shown to be viable alternatives, offering fairly matching results at the individual building-level and even closer predictions at the level of ensemble regional fragility curves that incorporate both inter-building and intra-building uncertainties.