Base isolation issues in Italy: Integrated architectural and structural designs

This paper deals with the evolution of base isolation design in Italy, underlining improvements that occurred in the last 30 years, from earliest pioneering cases to recent solutions. They result from an integrated design procedure into which structural and architectural aspects merge harmoniously. Back analysis of existing structures and personal assessment of corresponding data from literature will give the possibility to describe changes occurred in Italian design applications. This paper looks at “all rubber” solution, matching the main design issues: design vibration period, Tiso; design displacement, δ; device diameter, φ; device tributary area, A. Following excursion will underline a quite different design approach, as compared to worldwide trends. Design displacements smaller than 30 cm, accomplished by device diameter in the maximum range of 900 mm–1000 mm, correspond to high vertical stress σ upon devices, up to 9 MPa–10 MPa, and to small vibration periods, not exceeding 3.0 s. In the last part of this paper, recent base isolation solutions, coming from a personal research path [De Luca et al.], will be analysed as result of a newer design approach. These latter cases will show benefits obtained through the increase of device diameters, φ, and corresponding tributary areas, A, combined with the reduction of the number of bearing points. This correspond to the use of on long-spans structural grids that guarantee greater flexibility also in organizing spaces. This underscores base isolation as part of an integrated procedure where freedom in architectural design combines to structural efficiency.