Análises numérica e experimental das pressões em silos verticais de fundo plano com diferentes relações altura/diamêtro (H/D).

Abstract

In the global economic situation, the vertiginous growth of production and exports of the agroindustry and food sectors in Brazil, consolidates the country as a fundamental role in the sector, mainly of soy and corn commodities, however, the storage deficit configures one of the challenges of the chain productive. In this context, metallic vertical silos are presented as alternative solutions for both industries and agricultural producers. However, silos are structures that can present high structural failures, especially due to the diversity of variables that affect the behavior of stresses and deformations in the walls and bottom. The objective of this work was to evaluate the pressures exerted by a granular product (corn) on the smooth walls of a vertical silo, for different height and diameter ratios (H/D equal to 1, 2 and 3, respectively) and concentric flat bottom. Static and dynamic pressures were evaluated in a pilot silo, whose design is based on the principle of Pieper and Schütz models used as standard by the German standard DIN 1055-6 (2000), with a total storage capacity of 2.35 m3. Based on the experimental results, the overpressure coefficient was experimentally determined for the studied configurations. To obtain the physical and flow properties of the product, tests were carried out using translational shear equipment combined with a shear cell called Jenike Shear Cell (TSG 70-140), according to the methodology recommended by the British Materials Handling Posterior Board - BMHB . From these experimental pressure results, the values can be compared with the main current foreign standards (ANSI/ASAE EP433.1:2019 and EN 1991-4:2006) and theoretical models (Rankine-Calil (2005) for low silos and Jenike et al.(1973) for slender silos, making a comparison between the main pressure prediction methods.Later, a numerical simulation was carried out, using finite element models (FEM) to evaluate the pressures normal to the wall. The numerically obtained results were compared with the normal pressures on the silo walls obtained experimentally. This information is important, as it is necessary for the design and development of silos, aiming at the integrity of the structure and equipment during the processing of products, for different combinations between H/D ratios and unloading forms. The data obtained experimentally present a substantial contribution. It is concluded that the Rankine-Calil formulation is the most indicated for low flat bottom metal silos and the Jenike formulation is the most suitable for flat bottom slender metal silos (H/D=3). Regarding the comparative analysis of foreign standards and experimental data, it was found that for the dynamic phase, the horizontal wall pressures can exceed those obtained by the calculation method proposed by ANSI/ASAE S433.1 for the ratio H/D = 2, for silos whose H/D=3 ratio, among the norms analyzed, the EN 1991-4:2006 adjusted better to the experimental data. The overpressure coefficients obtained decreased along the height of the silo. The