Earthquake protection of the Torre Grossa medieval tower of San Gimignano, Italy by vertical external prestressing

This paper presents an application of a methodology for the seismic vulnerability reduction of masonry towers by reversible prestressing. The approach is applied on a medieval tower located in San Gimignano, Italy, which is considered as a world heritage site. The 3D FE models are calibrated with experimental data and assessed by nonlinear static analyses including the seismic demand of the site and an accurate validated masonry model. The vertical prestressing is applied at key points identified in the seismic vulnerability assessment. This technique is in compliance with the demand for architectural conservation because it may be fully reversible. The seismic performance is enhanced by increasing force, displacement and internal confinement. It is observed at ultimate limit conditions an upgrading of 14.3% of displacement with the medium prestressing level and 9.5% with the high level. The results are analyzed and discussed in terms of earthquake energy dissipation and failure mechanisms.