Response the Cylindrical Elevated Wheat Storage Silos to Seismic Loading

Abstract

The elevated cylindrical storage silos are lifeline structures and strategically very important, since they have vital use in industries. Silos are special structures subjected to many different unconventional loading conditions, which result in unusual failure modes. In addition silos are cantilever structures with the material stacked up very high vertically. The earthquake response of silo structures for the storage of bulk solids differs for elevated silos and silos supported directly on the ground. The walls of different type of silos are subject to earthquake loads from the stored mass, and these may substantially exceed the pressures from filling and discharge. The assessment of horizontal action of ensiled material due to seismic vent seems to be particular interest. This paper is concerned with the earthquake response of these structures, which has received little attention to date. A cylindrical silo wall and bulk solid is modeled by three dimensional finite solid l elements. The interaction effect between the silo wall and bulk solid is taking account by using the nonlinear approach proposed by Duncan and Chang. A then interface layer proposed by Desia is applied to describe the phenomena taking place on the surface between the granular material and silo wall. Coulomb's friction low was used for modeling of wall friction. An incremental iterative finite element technique is applied for dynamic analysis of wheat silos using SAP2000 structural software package. In this research seven reinforced concrete silo models with different height to diameter ratios were studied and analyzed in time history by using earthquake acceleration 0.5g applied to silos models. The resulting finite element silo pressures as the silo is full with and without earthquake excitation are compared with theoretical filling and discharging pressure. The result obtained revealed that the elevated silos response is highly influenced by the earthquake characteristics and is depending on the height to diameter ratio. Also the findings indicate that the squat silo (large diameter and height) are more resistance to the earthquake and more economical. The seismic responses of the elevated wheat silo such as top displacement, normal forces, shearing forces and bending moments in silo support have been assessed for earthquake records.