Pilot-scale test stations make it possible to obtain reliable and comparable results applicable to full-scale systems by conforming to specified proportional limits. Therefore, in this study, normal and frictional pressures were evaluated in a pilot-scale test station composed of a slender cylinder silo using maize, a free-flowing product, as the stored product. Temporal effects were analyzed and verified during filling, static, and discharge conditions. The maximum normal and frictional pressures were also evaluated. The results were compared with ISO 11697: 1995. During filling, accommodation peaks occurred only in the α: 30° hopper. In general, normal pressures were higher for the flat bottom whereas higher frictional pressures occurred for the 30° hopper. The maximum experimental pressures (normal and frictional) were lower than those provided by ISO 11697. Therefore, it is concluded that the coefficients used in the ISO standard are sufficient to promote safety in silo projects.
Silos are used worldwide to store granular and powdered materials. Agricultural, food and feed products are commonly stored in silos. However, many questions remain unanswered about how to estimate the pressures applied by the bulk material, which are needed to design and calculate the structure of the silo. The complexity of the laws that govern the mechanical behavior of the stored material along with the low number of experimental stations in the world hinder progress in this field. The aim of this study was to elucidate the relationship of the hopper angle, flow pattern and vertical stress at the cylinder-to-hopper transition in slender silos. Therefore, a set of experiments was conducted on a test station to measure the vertical stress produced by maize at the cylinder-to-hopper transition. Five different hopper angles were used. The experiments comprised the filling, the static phase and the discharge. The results obtained show that the hopper angle influences the vertical stress at the cylinder-to-hopper transition. Some bottom configurations (flat bottom and bottom with an angle of 30°) led to vertical stresses that exceeded the value calculated according to Eurocode 1. It is clear that further experimental studies are still necessary to understand the underlying physical phenomena and the relations between pressures, silo geometry and flow pattern of the stored material.
The building construction is responsible for the largest industrial sectors in the world, with high energy demand and use of natural resources. Given the scarcity of natural resources and the energy crisis, the use of waste in building materials becomes a target. Therefore, this study aimed to evaluate different treatments with pine sawdust and coffee husk additions, both at 10% by mass and also evaluated in drying and burning. The treatments were evaluated by bulk density, linear shrinkage and compressive strength. In the treatments without burning, it was possible to verify that the addition of 10% of residue reduces the mechanical resistance of the material considerably but improves the physical properties. In the burned materials, it was observed that the addition of residues is unsatisfactory due to the high temperature, carbonizing them, increasing the porosity, thus destabilizing the material, negatively affecting the physical and mechanical properties.
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