Analysis of the dynamic behavior of squat silos containing grain-like material subjected to shaking table tests

This paper reports the outcomes of a series of shaking table tests performed at EQUALS lab of Bristol University in the framework of SERIES project. The experimental test campaign was devoted to the evaluation of the effective behaviour of grain in flat-bottom silos full of grain during an earthquake. This research work starts from all the same basic assumptions of Eurocode 8 except for the one regarding the horizontal shear forces among consecutive grains. Only this difference leads to a new physically-based evaluation of the effective mass of the grain, which horizontally pushes on the silo walls. The analyses are developed by simulating the earthquake ground motion with time constant vertical and horizontal accelerations and are carried out by means of simple dynamic equilibrium equations that take into consideration the specific mutual actions developing in the ensiled grain. The findings indicate that, in case of squat silos (characterized by low, but usual, height/diameter slenderness ratios), the portion of the grain mass that interacts with the silo walls turns out to be noticeably lower than the total mass of the grain in the silo and the effective mass adopted by Eurocode 8. Two series of tests have been performed with two different heights of the ensiled material to simulate a silo more or less squat. silo. The ensiled material has been modeled with ballotini glass. In the paper, the silo model for the first and second test is presented, and then the dynamic behavior of the structure is described with reference to the two series of shaking table tests. The results indicate that, in the case of squat silos the portion of grain mass that interacts with the silo walls turns out to be noticeably lower than the total mass of the grain in the silo.