Pressões em silos verticais cilíndricos metálicos: determinação experimental e cálculos teóricos por normas estrangeiras.

Abstract

The grain flow is a dynamic phenomenon that presents nonlinearity, responsible for the occurrence of structural problems in silos, assuming particular interest in Brazil because the country does not have a design standard of these structures. The aim of this work was to overcome this limitation by evaluating the pressures by instrumentation of a silo in true magnitude and using three foreign standards, EN 1991-4, ANSI/ASAE EP433 and AS 3774. The instrumentation was made by load and pressure cells along the walls, bottom and uprights of the silo. The horizontal, vertical and trawl pressure profiles were obtained during the loading, storage and unloading phases of corn grains. The vertical pressure distribution in the silo bottom was shown to be variable along its radius, according to the code AS 3774 formulation, alternative to the simplifying hypothesis of uniform distribution of the others. It was also observed experimentally the non-occurrence of overpressure, corroborating with the EN 1991-4 and the ANSI/ASAE EP433 standards for the flow type of this analysis. The horizontal pressure change with the height of the silo indicated that the American code underestimates the efforts and the European and Australian standards give values close to each other and to the experimental ones. The K coefficient showed to be variable during the flow, reflecting change in the stress state for the passive condition at the discharge. The charge transfer to the uprights was 35%, being that ANSI/ASAE EP433, EN-1991-4 and AS 3774 codes increased the transfer by 8.34%, 60.30% and 143.62%, respectively, reflecting divergence between these prescriptions, which highlights the importance of seeking a normative code applied to the Brazilian reality.