Reducing the seismic vulnerability of existing elevated silos by means of base isolation devices

Industrial silos are used for storing a huge range of different materials. In the last decades, many of these structures were damaged by natural events, among which the earthquakes were the most significant. Indeed, numerous industrial plants have been built in the territories with high seismicity risk. Most of these plants have been designed and built before the latest updates of the seismic design codes took place, hence their current seismic reliability is questionable. In order to avoid future economic, life-safety and environmental troubles that can be caused by the collapse of these non-building structures, specific retrofitting solutions should be developed and implemented urgently. This paper shows the feasibility of the seismic isolation solution on a typical case study. Seismic vulnerability of an existing industrial steel silo system has been investigated, and a retrofitting solution has been proposed making use of the curved surface single sliding pendulum devices. Incremental dynamic analysis method has been used to compare the performance of the original and the retrofitted solutions. Structural benefits of the seismic isolation solution have been quantified in terms of inelastic deformations, base shear, inter-story drifts and isolator displacements. The seismic behaviour of the original and the retrofitted structure has been compared by means of fragility curves.