Seismic protection of industrial gas tanks using base isolation system

Abstract

The present paper describes the numerical studies carried out on a big gas tank storing gas released by a furnace. This Gasometer, constructed in the early eighties, consists in a steel cylinder of 70m height and 44m diameter. The tank bearing structure is composed by a classical steel frame closed with curved steel plates. Inside the tank, a piston-fender and rubber sealing system allow the variation of the container volume and control the gas pressure. The seismic vulnerability on its as-it-is state is assessed through the execution of numerous Incremental Dynamic Analyses (IDAs), placing particular attention on the definition of possible limit states. Among the several possible seismic upgrading strategies, the adoption of base isolation system is then studied. To accomplish the latter, the Double Curved Surface Slider (DCSS) was selected amongst the available options. The results obtained on the gasometer and the comparison between, the as-it-is state and the retrofitted state, supplies important information about the effectiveness of base isolation for the risk mitigation of gas tanks. Furthermore, a linear design method for determination of the design displacement of the isolation device, proposed within the referred project, was verified against time-history nonlinear simulations.