ANALYTICAL DEVELOPMENTS AND SHAKING TABLE TESTS ON DYNAMIC BEHAVIOR OF SQUAT SILOS CONTAINING GRAIN-LIKE MATERIAL

For the seismic design of flat-bottom grain silos containing grain-like material, the Eurocode 8 suggests that the horizontal actions on the walls of the silo are evaluated under the hypotheses of (1) stiff behavior of the silo and its contents and (2) the effective mass which pushes on the walls corresponds to the whole content of the silo except the base cone with an inclination equal to the internal friction angle of the grain. This design approach seems to be overconservative for squat silos. In a previous research work, the authors developed an analytical study, which allows for substantial reductions in the seismic actions for silos characterized by squat geometrical configuration. The analyses are developed by means of plain dynamic equilibrium considerations and by simulating the earthquake ground motion with constant vertical and horizontal accelerations and lead to the subdivision of the ensiled material into three different portions. The findings indicate that, in the case of squat silos the portion of grain mass that interacts with the silo walls turns out to be lower than the total mass of the grain in the silo. Shaking table tests are currently under development at the lab facilities of the Bristol University, under uniaxial constant, sinusoidal and earthquake input.