Pressures in squat steel silo with flat bottom storing maize grain

Abstract

Squat steel silos with a flat bottom are used worldwide on farms to store granular products with high commercial value, especially soybeans and maize. However, many questions remain unanswered regarding storage and estimation of pressures in squat silos. In addition, there are few full-scale experimental stations in the world to facilitate the study of silo pressures, hindering progress in this area. The objective of this article is to analyze the pressures in a pilot silo test station obtained from tests performed using free-flowing product (maize). The results obtained were compared with Eurocode 1, part 4, ANSI/ASAE S433.1 and the Rankine-Calil model. The filling height of the product used was approximately 0.75 m (H/D ratio equal to 1), considering a flat bottom configuration with concentric discharge. Pressures were evaluated in the filling and discharge stages. Normal and friction pressures in the silo, overpressure coefficient and stored product weight were recorded. The results obtained show that research advances in the area are urgently needed for squat silos. The horizontal pressures showed peaks that exceeded the standards: Eurocode 1, part 4 and ANSI/ASAE S433.1. Only the Rankine-Calil model was adequate compared to the values obtained experimentally. Friction pressures were not consistent with values theoretically obtained by Eurocode 1, part 4 and ANSI/ASAE S433.1. An overpressure at the bottom of the pilot silo was observed. It is suggested that the overpressure coefficient be considered in the calculation of pressures in the dynamic stage.