Análise de pressões em paredes lisas de silos cilíndricos verticais.

Abstract

The study of the pressures that the stored product exerts on the silo walls is a determinant factor in the knowledge of the causes of failures, ruptures and vertical silo tipping. Thus, the objective of this work was to determine, empirically and experimentally, the pressures along the walls of the vertical metal silo exercised by the stored product and the influence of the H/D ratio in the representation of these pressures. For the determination of horizontal pressures and friction, devices consisting of pairs of load cells were used, fixed to square sections of the flat wall silo that had dimensions 2.5 m body height and 0.64 m of internal diameter and hopper with 0.51 m of height and inclination of approximately 60 ° with the horizontal, made of flat steel with 1 mm thickness. The devices with the load cells were fixed the section of the wall and a vertical rod in steel, thus allowing the acquisition of the strength exercised links grains for the calculation of the lateral pressures along the structure of the wall. The corn loading and unloading assays were in quintuplicata, and three consolidation times were adopted, being those of 6, 12 and 24 hours, in addition to the instantaneous assays. The pressures determined experimentally were compared to the values found from the equations contained in the standards AS 3774 (1990) and BS EN 1991/4 (2006). Four H/D ratios were also used to calculate the pressures where each height was determined by the ratio of 1, 2, 3 and 4. By results, it was evidenced that the experimental data of horizontal pressure during loading were up to 70% lower than the normalized, considering that the norms increase the values due to the use of safety coefficients and, although the calculations were performed with the subtraction of this coefficient, the experimental loading pressures remained inferior to the normalized ones. The experimental friction pressures during the unloading of maize were approximately 400% when compared to the loading, but also inferior to the normalized values. In the H/D ratio, the smaller this ratio was the horizontal experimental pressures, as well as more distant from the normalized values these experimental values were presented.