Seismic retrofit of industrial silos by means of base isolation devices

Abstract

Silos are industrial facilities used for storing a huge range of different materials. In the last decades, many silos were damaged by natural events, among which the seismic events are the most significant. Indeed many plants are located in territories in which seismic risk is not negligible. Furthermore, most of these plants have been designed, and built before the latest updates of the seismic design codes took place, and most of them are prone to earthquakes. In this study, seismic behaviour of an existing industrial steel silo system in Italy has been investigated, and a retrofit solution has been proposed making use of seismic isolation technology. Curved surface single sliding pendulums have been designed as a base isolation retrofitting solution. Incremental dynamic analysis method has been used in order to evaluate the seismic performance of both the non-isolated and isolated cases. Structural benefits of the seismic isolation retrofitting solution has been quantified in terms of inelastic deformations, base shear, floor drifts, isolator displacements, and residual drifts, and comparisons between the original and retofitted solutions are presented. The impact of vertical ground accelerations on the global behaivour of seismic isolated silos has been highlighted, which showed that a fully elastic superstructure behaviour can be achieved only when the vertical component of earthquake is not significant. Uplift has been investigated and stated as a limiting parameter for the design of seismically isolated silos. The study has been realized thanks to EU-RFCS research fund for PROINDUSTRY project [1].