Arch effect in silos on discrete supports - Is it a myth or reality?

Steel silos are interesting, complicated facilities. In order to assure its complete emptying by gravity they are often placed on supporting frame structure above the ground. Values of stresses in joints between thin walled shell and supporting frame elements are very high. It can cause the local buckling in the shell. The simplest way to design steel silos is to divide hypothetically the cylindrical shell into two parts - ring beam, supported in some points and shell above, uniformly supported. This conception is accepted by European Standard EN 1993-4-1. The particular moment is that the ring beam and cylindrical body above it are separated. Actually the two elements are jointed and work together in the same time. Considering the last results of Zeybek, Topkaya and Rotter from 2019, and as well as his own research, the author asks the question if it is true that the transferring of discrete base reactions to the cylindrical body is done by bending work of the ring beam, which is the conception in EN 1993-4-1? Or the vertical reaction forces are actually redistributed on the height based on the work of the cylindrical shell under compression as an arch. Using the contemporary capabilities of the programs for spatial analysis of building structures the author will try to find the answer of this question

Vertical stiffeners and internal pressure - influencing factors on distribution of meridional stresses in steel silos on discrete supports

Steel silos are interesting, complicated facilities. In order to ensure unloading of whole amount of stored product by gravity, they are often placed on supporting structure. Values of stresses in joints between thin sheets and supporting frame elements are very high, which could cause local loss of stability in thin shells. Many researchers have worked on values and distribution of the meridional stresses in that joints. Their traditional approach is to divide in their minds cylindrical shell on two parts - discretely supported ring beam and continuously supported shell above it. As a result of their efforts critical height of shell Hcr and ideal position of intermediate stiffening ring on shell are determined. The scientific results are based on semi-membrane theory of Vlasov, in which influence of vertical stiffeners and internal pressure is not accounted. On other hand all steel silos are loaded with an internal pressure and majority of them have vertical stiffeners above supports. Is it possible the obtained scientific results to be applied to these silos? In a present article the author will show that stiffeners and pressure should not be ignored in an analysis

Wind loads on girder bridges

Bridges are facilities that are in exploitation outdoor. Often the wind is the leading horizontal force in the transverse direction. Therefore the bridges have received the due attention in the standards for wind loading. Unfortunately, in all available standards for wind load on the bridges, one, summarized value of the aerodynamic coefficient is indicated. It is related to the entire cross-section of the facility. There is no differentiation for the individual longitudinal girders and/or roadway. Information about the specific wind pressure on each of the bridge’s element is required for the correct design of their supporting systems, whether they are framed or braced type. To fill this gap, the author has built several models of bridges with longitudinal girders, using a Computational Fluid Dynamics (CFD) analysis. Through them he determined the values of the aerodynamic coefficients for each of the bridge girders under the roadway and the cross-section of the bridge as a whole. Conclusions are summarized and the results clearly show the values of the aerodynamic coefficients for the whole section of the bridge are with 50-60% lower than the ones reported for the windward girder