Intermediate Isolation System for Adding Floors in Existing Buildings: Chart-Based Design

In this paper, the addition of extra floors to existing buildings is suggested as a strategy able to increase the usable surface area offered in historic city centres with almost no land consumption, and, contemporarily, to improve the seismic response of the building structures. Starting from the definition of IIS spectrum for exploring the design effectiveness of this solution in the elastic case, a design framework and a five-step chart-based design procedure are suggested for utilizing IIS design spectra also in the case of existing buildings with inelastic behaviour. The procedure is validated by contrasting the outcome of the application to a case study to the numerical results obtained from NTHA of thirty-five 2DOF models, representing thirty-five design solutions for the isolated vertical extension of the case study. Extension and generalization of the procedure are also briefly discussed, considering different shapes of code design spectra.