REFINEMENTS ON SILVESTRI’S THEORY FOR THE DYNAMIC OVERPRESSURES PREDICTION OF FILLED SILO SYSTEMS

Silos are strategic structures widespread in the industrial sectors for post-harvest preservation purposes. Silo structures are historically classified as non-building structures by most of the standards, in which their size and storage capacity might range from twenty tons reaching up to thousands of tons for a single silo. They are also different from liquid tanks. The stored granular material plays an essential role in both static and seismic design. The material unit weight, the lateral pressure ratio, the angle of repose, and the friction coefficients of stored product with the silo wall as well as with the silo base, strongly affect the dynamic and seismic response of such structures. Different analytical formulations for evaluating the additional pressures exerted by the ensiled granular material onto the silo wall under seismic excitation were developed, originally by Trahair et al. (1983) and more recently by Silvestri et al. (2012). Experimental shaking-table tests performed on silo specimens showed good agreement with the latter formulation for squat silo categories but within some limits of validity related to the filling height and seismic input magnitude. This has encouraged a revision of the original theoretical framework in order to extend it to the cases of intermediate and slender silos, which is the object of this paper. The analytical developments are carried out by means of simple free-body dynamic equilibrium equations and provide an attempt to merge and join the two theories through a new formula for the dynamic overpressure values beyond the Silvestri theory's validity limits.