New steps towards the knowledge of silos behaviour
F. Ayuga 1
P. Aguado 2
E. Gallego 1
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Escuela Técnica Superior de Ingenieros Agrónomos, Polytechnic University of Madrid, Spain
Escuela Superior y Técnica de Ingenierías Agrarias, University of León, Spain
Int. Agrophys. 2005, 19(1): 7–17
The structural complexity of silos has been object of interest for engineers and researchers for more than a century. During years, mathematical models have tried to describe the problem with as less simplification as possible. Meanwhile, experimental tests in silos have been conducted in order to simulate reality. Phenomena are not yet well understood, but researchers have better analysis tools every year. The Spanish research team is now trying to provide some relevant result to the international community of silos researchers. This is the reason why finite element models are being improved. The filling and discharge phenomena as much as eccentricity influence are simulated to better understanding the silo behaviour. Commercial computer software with high capacities have been chosen to get an accurate simulation of the mechanical behaviour of the bulk solid, the silo wall, the contact between them and the dynamics of the phenomena. At the same time, difficulties have been found to apply these models due to the lack of knowledge existing about the mechanical parameters of the bulk materials that are required by the theoretical models. So an ambitious set of bulk materials tests have been designed to get such parameters with enough accuracy. Nowadays the simulation of silo explosions is not one of the research team objectives, however tests include determination of parameters of the bulk material related with the analysis of explosions, which anyway are necessary to a proper design of installations for protection and prevention. Finally, three experimental silos have been erected. They are cylindrical of 1.9 m in diameter and 5 m in height of the vertical wall, with emptying hoppers designed with three different eccentricities. The wall has been made of smooth steel, with enough thickness and reinforcements to be considered rigid. Specially designed sensors have been fixed in these silos, in order to measure the horizontal pressure and the friction force between the wall and the bulk solid. The horizontal pressure cells measure the deflection of a circular thin plate by means of four strain gauges, and the friction forces sensor measure the deformation of a small cantilever beam by two strain gauges. Although the research work is now in progress, the first results are hopeful and our research team wish to help in better understanding of these interesting structures.